Building shadows in the face creating background effects - both elevate your paintings significantly. Background - my favorite effect lately has been just plain old spray bottle with water. Get one that creates heavier splatter - let your background wash rest for 2-3 minutes (until it starts to get a little matte, but it is still damp) and than spray from some distance to get larger effect. Shading the face - all you need is a mixture of red and cobalt blue, some deeper shadows will be more blue