The populists at Valve have a new blog just for the Team Fortress 2 community, and explain:
Our hope is that we'll be providing you with a variety of interesting things to read, whether you're a hardcore TF2 player or whether you've just started. We'll be going into the details behind some of the gameplay, posting a bunch of the concept art we haven't released before, and showcasing the great content the community is creating.
Ooh! Up now is concept art for the flare gun, showing the different ideas that were considered before gameplay made the final decision. Watch that space, then, for more behind-the-scenes peeks.
TF2 Official Blog [Valve]