Just a suggestion to add to what Foster mentioned. You have a pot helmet hanging from one of the spare links holders and it doesn't feel right for it to be there all by itself almost magically suspended IMHO. There isn't any other stowage around it and it's a rather strange place for it to be considering the crew would have kept something like that inside if at all. The tank is buttoned up and muddy, giving the impression it's "on the move" and the helmet would most likely not stay in place under those conditions.
I like the base and the weathering, very nice match up with the vehicle. For an added sense of realism, add some weathering to the barrels since they are relatively close to the road and would be splattered, rusty, etc. from routine exposure.
Good luck at contest and be sure to let us know how you do!