Hmm, I may see a couple problems here.
I think that there are two potential problems here. I say potential because the one may actually cause the other one, but it's hard to tell. The picture is actually very busy. Perhaps a little too busy for the eyes. There's so much going on in the main picture and no real focal point.
Maybe it isn't too busy content wise though. I think it's more about the amount of black in the room. All this black makes it hard for the viewer to tell what is what. It might be better to remove a couple of characters in general or maybe even just get rid of the black and white checkered patter on the floor.
Overall, the characters are done well, the picture looks pretty cool all in all, but it's really too busy to be a "great" piece of art in my opinion.