For some reason I've always hated that picture of Seto, he looks so weird. xP
You made your sigs very big, try making them a bit smaller and see how you like it.
The text looks very strange there, it's yellow and really fancy. o.o
I suggest downloading some new brushes or something, the background looks very plain, and I think it'd be better if you found a picture of both Mokuba and Seto together.