hi, i would use the pokemon powers to fill in the background and collage(spelling) it. so charmanders fire would spread behind everyone and pikachu would having lightning behing that above him etc like layers up the arm if you know what i mean?

at the base of arm you have ash standing on grass then a bit of thunder and lightining behind them for pikachu then fire behind charizard and that bird thing with loads of zzzzzzz swishing around the sleeping one etc see if you could get a photoshop.

also where people have jap sleeves they have cherry blossoms..you could use pokeballs and pokemon trading cards