you developed a decent grunge style there well done

on the first onew the renders are very well blended but it has no colour so try adding some colour to it. on the second youve blended the render well again and the bg is coloured but you need more veriation between the tones on the bg on the fird one the render isn't as well blended as they are on the other two sigs so just blend it slightly around a few of the edges and add a little more colour to the bg even if its just a tint just so it matches the render a little more and that will help to blend it a little more

overall there all good much better than you current so keep at it and try developin new styles