I wonder how successful of a lasting revenue stream this will be versus the TF2 model. Sure it has plenty of purely cosmetic weapons/hats/accessories, but a lot of items in TF2 affect the actual gameplay through custom stats/modifiers. The visual design of the game also makes it much easier to notice the different kinds of things people are wearing (size of character in relation to the screen, killcams, etc).
You don't really see characters in Dota 2 with any kind of detail like TF2, and since they're refusing to limit hero availability in any way or have custom items (all good decisions), I wonder how popular hard to notice cosmetic changes will be. Visual items on character models might as well not exist given their size and the pace of the game, no one's going to have the time or desire to zoom in to look. And I worry that changing hero skins too drastically will reduce the ability of players to instantly recognize heroes at a distance.
I look forward to seeing how Valve creatively addresses these kind of issues.
I can see Valve drawing from their own game series to release stuff like:
New Announcer voices - Take any character from a previous Valve game (GLaDOS, Francis from L4D, Heavy from TF2) and replace the default announcer with them. I personally am sick to death of the original announcer, and would love some options.
Minion/Building skin pack - Replace the minions/buildings with TF2 characters. Demoman = catapult, Sniper = ranged, Pyro = melee. Towers could become TF2 engineer turrets, start at lvl 1 and progress to lvl 3 as the game goes on and they get stronger. Or replace towers with Portal Turrets that say "Sorry!" when they kill you.
Courier skins - Pretty sure they've already announced something like this. Change the donkey into other animals, characters from Valve games (a smart mouthed Scout courier would be cool), miniature versions of characters in DOTA2.
Character skins - As has been mentioned, Riot made TONS of money on skins for heroes (I spent more than I care to admit on skins in that game....), it can be done so that you can still recognize the character, but don't take away from their quick recognition in the heat of battle.
I'm sure Valve has this all figured out, I look forward to seeing how they implement things.
