I think Meggedo's comment is very valid. Certainly, it's not necessary to use a trunks pic if you are making a sig, but if it's a DBZ sig, I think that anything else would be odd. I'm of the opinion that design should be, well designed, that is to say that it has logical coherence. There is something that ties it all together. So if you make an "Evil Trunks" DBZ sig, it would make some sense to have a picture of a Trunks that was evil. And depending what tone you want that sig to have, the font should match the intention. So if you use Comic Sans for example, I'd say a comical approach to "Evil Trunks" would be appropriate. Say a chibi-Trunks with horns and a pitchfork, possibly cartoos fangs as well.