If you are talking tilesets you could easily change the tiles, but that’s on the tileset people. As dev’s we do literally nothing with the tilesets other than providing the code-side support for them. We’ve already supported tile swapping, and now it’s up to the tileset people to have multiple human tiles that you can switch between if you want. (Heck, you could probably just create a “different race” weightless item for your inventory that changed your sprite right now if you wanted, I know that we already support equipment modifying your character tile). We might also support tile changes on mutations (in which case you could mod in a mutation to change your tile to the appropriate race) but I’m not sure, and if we didn’t it shouldn’t be much of an extension from the current clothing tile support.
As for ASCII, the @ isn’t white because it has white skin, it’s white because that’s the most visible color. NPC’s are pink because that was another rather visible color that wasn’t white. It has literally no connection to race in the slightest. Similarly the only place that gender exists is in the professions name and in character random name generation. There is absolutely no difference between an PC that picked a male profession and then changed clothes and one that picked a female profession off the bat, and even most professions can’t be seen once the game has actually started. If you want to play an intersex person you are totally free to, we specifically avoided handling gender anywhere in the code precisely to allow for options like that. There is nothing saying that your Punk Rock Girl can’t be trans, and it’s like that on purpose. 
