Looking pretty solid so far. The barrel instancing is a bit front and center now, not sure if you plan to add more textures. A quick master mat with and a couple instances with a multiplier on the diffuse to get some darker and light barrels would break it up nicely.
Alright try this. make this into a shader! I made a shader like this.....a long time ago. tiled Noise + Lerp (Reverse Rim Light) added to the diffuse/spec (spec optional). It will really help sell that spray painted feel. I hope you try this I think it could look really sick with a shader like this on here.