I agree with mike as well. This at the moment screams maya procedural texture to me
how about using that texture (which i think is quite nice, although there is more rust than oil drum left!
) and controlling it using painted greyscale maps to achieve what Mike was talking about. The best way to do that is to think about how these barrels would be used in real life, the edges would be knocked and scrapped from being dragged around, you might have some dents in the side where it's been dropped etc. All of these things add to the feel of the realism in the image and help to tell the story of why the barrels have become like they are...
Technical Director - Framestore
Currently working on: Your Highness