Here’s a rusty barrel I made. The textures (and material) are all procedurally generated using nodes. I then exported the diffuse, specular, and normal maps as images and created a glsl version, which looks pretty much the same as this render here (complete with normal-mapped peeling paint). You can download both versions at this link.
This model is free for noncommercial and commercial use, provided you credit me and put a link back to OpenGameArt. 
I’d love to hear any thoughts people have.
Peace,
Bart