Mmk, my honest opinion is that when you just put a bunch of characters in front of a background, it looks SOOOOOO bland to me. Alright, first of all scale down Wolverine a little bit, because he looks wayyy bigger than the other guys. Next move Gambit just a tad but up and a little more to the right, you could do the same with Wolverine and it'd look just right. The heads and eyes are just about perfectly aligned though which makes it look nice.
Next, get rid of Sabertooth in the middle, because the middle of a picture like this where you have 2 opposing teams, you wanna have something breaking them, or pushing them away, and making your eyes do a triangle effect. Next what you want to do is either find a picture of Sentinel, Magneto, or some other very evil looking character that will be blurred in the center. The best way to get a good looking effect for this, is to first put the center character in the middle, and make him so he takes up the entire background, then go to Filters: Blur: Radial Blur and select Zoom Blur, and modify to your liking. When you do this, the center of the character will be focused, but all of the rest will be pushed towards the edges. Also, turn down the Opacity on the background character.
If you want an even more dramatic effect, duplicate each of the character layers, and line them up so they're exactly entered with the copied layer, and put a zoom blur on those background pics also, which will give the characters a real prodominant look *spelling rules*
-Just a thought
-CthulhuLuke