You can't disguise while not in a TDM team, which seems odd. You should be able to as long as the minigame itself has teams.
Walking about with a knife in hand while "disguised" is very suspicious. It should disguise your weapon too and I believe this is possible with clever mounted images.
Updating the minigame settings will revert everyone to team uniforms.
Going to the Avatar menu to change your settings via default game menus (for instance, I want to disguise as a Red team player with a black head instead of yellow to look like their Sniper) will instead revert you to team uniforms.
Using an Invisibility Watch while disguised will revert you to team uniforms when you uncloak, which does not happen in TF2. This is not my fault because I am using default game methods which would fix the above problems if you packaged.
With uniforms reverted by the above methods, you then cannot redisguise until you fire a weapon. ("You're already disguised as this team!" even though you appear as your team)
