If you choose to paint it...
A well-made stencil (get out some card stock or posterboard and an X-acto knife) and some acrylic paint can do wonders. Make sure your stencil is right up against the fabric. Use a foam paint roller to apply the paint-- Make sure it's well soaked first.
If you do this method (or spray paint), be careful not to apply too much paint! It'll bleed up through the fabric under your stencil and make the art blotchy.