What are your personal headcanons? The things that aren't directly referenced in-game, but you choose to believe. I'll start.

The Cryptarch is suffering from the first stages of dementia, but he's still so very knowledgeable and talented that they don't want to fire him. Instead, they "kicked him upstairs" to deal with the Guardians directly while they handled the hard research. Funnily enough, he likes it this way.

The only class of Guardian that the average people of the City are familiar with seeing are the Titans. That said, it isn't necessarially a good thing; the Titans only ever show up during riots, or other bad situations that the police themselves can't handle. (Taken from a mention on a mark of Titans dealing with stuff like that.)

There's an almost-but-not-quite racism going on. While humans, exo and awoken are treated as equals, relationships between them are an unspoken no-go. There are select individuals in the world who are trying to change this, though -- there's so little joy in the world these days, why not foster any that you can?

Holiday is very much a tomboy, and shooting the breeze with folks is almost expected. But there's actually a reason why an engineering genius like herself is dealing with the Guardians instead of actually working. She's had a rather bad injury, and while they were able to graft on a new lower torso, it doesn't work quite right. It's easier for her to work with diagrams and deal with uppity Guardians than crawl through a ship's systems. (It might just be her model on the 360, but the way she sits is... Well, awkward to say the least. I'm not sure that it's even possible to sit like that in real life.)

Eva? Not human. Sure, she looks it, up until you look at her with the right filter. Then her eyes are almost pure black. All of the sclera is completely black, and you can barely make out the iris. Nobody knows what she really is, or how someone like her ended up getting permission to set up shop in the Tower. Cayle is suspected of pulling strings. But she's still eager to work and please, with no ulterior motives. (Again, might just be a 360 model glitch, but I see her eyes like that all the time. Dang creepy.)

Some people think that the postmaster is going to be retired (read: scrapped) soon due to faulty systems causing pseudo-neurosis. Even still, there's a surprising number of Guardians who will wander up to the frame and gently tell her to relax. That it's going to work out in the end. That she's worrying too much. The part that has the paranoid people worrying the most is that she's started to thank them rather sincerely.

Dead Orbit isn't stupid. They know that if they go beyond the Light of the Traveler, any Guardians with them are going to die. Maybe not immediately, but eventually they'll need Light to sustain them. When people approach them about it, they claim that they've been hoarding motes of light for just such an eventuality. That's only partially true. Those motes will only last for so long. They have a secondary plan in place. The Hive aren't the only ones who nabbed a shard of the Traveler. They'd rather not use it, loathing that they'd still have to rely on the Traveler for something, but they also aren't going to condemn the Guardians who help them into a slow and painful death. They may be many things, but whenever possible, they take care of their own, dangit.

The Crucible? Yeah, it's for training. Ostensibly. But that's not its primary function. After all, fighting other Guardians is far different from fighting the minions of the Darkness. Ever hear of "bread and circuses"? Think about that a minute. That said, the Iron Banner really is about training. The best get approached by Lord Saladin for a private meeting. Everybody always walks away from that meeting a little quieter, and a little more pale.

(CC10)

some stuff I've thought on, some stuff off the top of my head that feels right

Xur is something else, entirely. The Consensus and the Speaker more or less know what he is and why he is, or at least they think they do. They don't tell anyone because the ruckus and stoppage of goods and information that would probably happen, especially if they told people everything they know about the Nine, just wouldn't be worth it.

Tess Everis is just what you'd suspect: a person with connections, some of them unsavory. She keeps to herself and doesn't make waves, most people that know her like her, and no one can definitively tie her to anything that's that bad, so she's left alone.

Cayde wants to get back into the field, everyone with ears knows that. Few people know one of the biggest reasons is to test a weapon. He found the frame along with a few other parts and rebuilt it to his own liking with great care. On the rare occasions when he refers to it, it's usually as "my Sack of Doorknobs". Master Rahool, a man of many words who has seen his share of horrors second-hand, is reputed to have described it only as: "frightening".

The Speaker's big secret is that he has no big secret, at least not about himself. He has some skeletons in his closet, but nothing beyond the average City denizen. He hides his face for the same reason early Warlocks wore hoods, and because it's traditional; it just happens to backfire with some people because they don't trust what they can't see. The Consensus has some idea of how he communicates with/for the Traveler, which is good enough for them, and the Speaker's not lying about it, though he's very intentionally vague.
The giant Event-Horizon-engine-looking thing is mostly for show at this point. What's much more menacing is the small black pyramid behind the Speaker's desk.

Banshee, the gunsmith, is also what you'd suspect: he has a long and storied history that he can only grab pieces of at any given time. Lakshmi saw the Fallen burn London? He can top that ten times over; or he could, if he could remember the stories long enough to tell them. This and his attitude about it make him arguably the most well-put-together Exo in the Tower, psychologically.
He has a standing appointment to get a checkup from the metal up and a cold boot, basically once per human generation, which is he only dimly aware of until reminded. The Tower's Exo repairers think he may well outlast the foundation of the Tower itself.
He always makes it to the Deep Stone Crypt (or at least, he does now). He's given up hating himself for it. He's only told one person about it, though. He can't remember if it was Shaxx or Cayde.

The seemingly less-needed Frames have had distinguished service, such that Frames can, but they're not fit for most duties any more. Out of respect and attachment, instead of being scrapped-- or fixed, which would be much too expensive in terms of labor for the Frames in question-- they're given low-impact duties, often maintenance and not-strictly-necessary guard posts, with the most past-their-prime Frames doing things like sweeping and providing location and orientation services (which in effect means maps).
Most City dwellers, including the Frames themselves, know it's been possible for these tasks to be done more efficiently since before the golden age, but there are reasons to have these Frames where they are, which turn out to all be practical on some level. Floor-cleaners ("Roombas", as the ancients called them) and the like aren't high on the list of things to produce and fix in the City's limited factories and shops. The people that know these Frames like seeing them around. Because of their past service, every once in a while they'll say something interesting or even give advice. Lastly, they add to the feel of the Tower in a way that would be effectively impossible to replicate, so much so that minor legends have grown around these innocuous machines (the most prominent of these being, "When the Frames no longer sweep, the Tower shall fall").

I really, really like you ideas for Banshee. Like, seriously. It's pretty much how I feel about him; he's not just a vendor, he's someone worthy of the utmost respect. But one that you keep your distance from, partially out of that same respect, but partially because eventually he'll make an offhand comment or struggle to remember something, and it just plain old hurts you.

I love his characterization. He's easily my favorite NPC at the tower.

What's much more menacing is the small black pyramid behind the Speaker's desk.

Interesting thing is that he's got five of those things.

Interesting thing is that he's got five of those things.

Fifth race confirmed.

Ms. Levante is always asking for such ... unusual things for a clothing vendor. Why does she need scans of equipment or items from our enemies just to make new artwork?

Why does she have all that armor piled up in her alcove if it is not for sale?

Dead Orbit is making a fleet. Where is it? Do they have launch facilities elsewhere?

Shaxx seems to be dual purpose. Having guardians fight in suspect areas, broadcasting the feeds to the people below in exchange for advertising monies and equipment to serve as prizes. Or did you think all those came from his personal collection? "Where does he get those wonderful toys?"