1) What color is the “wall print”?
2) Consult your color wheel to see what will transpire by the addition of the color you are choosing. Here is a great set for artists click here.
3) When adding a stamp, stencil, or mask to the paint on the plate, choose a pattern that will enhance the print rather than dominate it. Subtlety is key at this stage and also allows for numerous layers each building more complexity to your print.