If this suggestion was already made, please tell me and I will delete this thread.
I was searching through the DF Wiki and I noticed there were no physical flags in DF. So I thought about suggesting it (and other things that I thought because of it).
The first thing would be the flag/banner + flagpole themselves. I think it would be interesting if we could have banners actually being held by dwarves into combat to increase morale and decrease the chance of fleeing. You could choose to put whatever image on the banner (or let it be random), or choose that it be the fortress or civ symbol. You could hang it on walls and on entrances to your fortress (similar to how you can carve walls, but these banners could be removed and the wall restored). I think it could be nice in a roleplay perspective and would give something else to do with textile which is nice [I like to raise sheep in my fortresses lol].
Tapestries would also be interesting, since with them we could adorn the walls of our fortresses with randomly generated things like when you carve it on a wall, but you could also remove it and relocate it to make more "themed" rooms and even sell these tapestries as part of the textile industry.
Finally, I'd like to suggest a simplified form of Blazonry for the description of symbols in game. I don't mean a revamp on the descriptions or anything. More like I think it would be nice if some key words or formats can be introduced in addition to what we already have so that a person could technically make something akin to Blazonry (aka Heraldic description) in their fort symbol. An example of that would be to add the word "field" and an interaction of something being "on" a field. Also letting everything in the description be colorable so one could for example say "a golden lion on a red field". That would basically be a golden lion with a red background, in Heraldry, but it can also be pretty easily understood simply as a literal lion on a literal field, making it flexible and understandable for whoever reads it. With that, one could also add a bit more descriptive positions and stances.
The DF Team definitely have a lot more important things to do now, but I thought it would be nice to throw this suggestion out here in case they ever see it and maybe, if they find it a good idea, to put it on their to do list for any time in the future lol