Valve has launched a new "contribution" system for Team Fortress 2, allowing players to create and upload avatars and items that could end up being used in the game.
It sounds simple enough: Make stuff, upload it and if it gets approval from Valve, it winds up in your backpack and gets added to the game's random item drop cycle. The new contribution system is strictly for models to avoid upsetting game balance, although players can still submit gameplay ideas for new items in the usual way, via email or on the TF2 forums. Once the new stuff starts rolling in, Valve will launch a gallery where players can view and comment on submissions.
To help get budding designers off on the right foot, Valve has also posted a few tips about creating items for the Team Fortress world. A consistent visual style is important, with nothing "modern, hyper-realistic or overly cartoony," and items should maintain character personality as much as possible. Model details can be slightly overscaled, underscaled or even removed altogether and designs should be kept "simple and clean, just enough to identify what an object is." Technical information about texture density, polycounts and other such things that I have no understanding of or interest in has also been provided.
Think you've got what it takes to turn your TF2 ideas into TF2 stuff? Show 'em you mean business at teamfortress.com/contribute.