before I say anything I think that this model in particular would have benifitted EXTREMELY with a nice high poly bake, and a spec and gloss map.
that being said, the textures could use a mega overhaul.
The ground is blurry as hell, don't really know why... either your images are really low res, or the UV space isn't distributed well. Flats would be cool.
The weakest parts texture-wise I believe are the bottom and the top. The harsh smoothing group seams aren't helping that situation.
The just need more dirt, grab some custom brushes and add some variation, add dust, cloudy dirt, and then beautiful texture overlays, and since there's no normal, paint some lighting!
the damage on the red thingy is pretty good, I wish that I could say that for everything else.
the grunge on the bottom is so uniform and obviously overlayed, go in with brushes and add and take away, add some color variation to make it more natural.
I think you're using just pure photosource, which isn't good...at all. And also, bake a lighting map and an AO map, I think that would be extremely helpful for you in this situaiton.
Hope this was helpful
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