I'm working on a more detailed FAQ, but here are some basic techniques you can request:
FADE - A spray of paint in the requested color. Can be whole print of top half, bottom third. Colors can be layered or stacked on top of one another.
DIP - A "hydrodip" or swirl of a requested color to produce a marbling effect. Looks great on top or underneath a fade.

Just type out your ideas in the requests field, and I can always message you if I need clarification. Each product here also has some sample custom orders, and the gallery section does too. 
LET'S MAKE SOME ART TOGETHER :)