Joe it looks very good. Here are some ideas that I had that may help.
1. Remove the kid in the upper right hand corner and slide the two other kids up and over to the right.
2. I don't know the type of Asian writting that is, but maybe put it in red and outline it in white. You might even play around with a bevel on the text.
3. Slide the two adult fighter up and over to the left, if you can with that picture.
4. Maybe make the background a gradient black to dark grey instead of solid black.
I like the poster and these are only suggestions. Good job!