I agree with Alpha, on the first gin sig there, try to dim the other characters or make them blend into the bg more so Gin himself "stands out" better. That's one way of adding more people in but not letting them interfere with what you want to enhance in the image ^^
The second one with only gin, Try to dim the colors on the bg a bit so it's not so bright, that would make gin show more.^^
The other two Kon and the girl (I never remember the name on ><) Perhaps some kind of shadow or outer glow on the text? (I actually barely saw there Was text on there until it was mentioned and I went back to check it o.O) Kon's sig looks really good though, I like it!

The girl, it seems to be missing something in that dark spot? Perhaps her name a bit faded in there?

What program are you using?
Hope you won't kill me for being honest in my opinions o.O Just trying to help and give tips on what may work ^^
*Is a Photoshop Junkie since 11 years (and counting) back* ^^