Signature size depends on usergroup and I don't plan to create new ones just for that.
Same with images there.

3-symbol names aren't allowed because they can't be searched for on forum. Game servers don't care about them, you can have a working 1-letter account.

Special characters, however, will make logging in with the game client impossible or will break customs downloading. If you want a non-working account I can make the name change - but why would you want it?