Take 4 canvases of each size), paint them a solid base color and add vinyl or stenciled design. stick decals onto canvases, paint the whole thing and then remove the stickers to reveal the wonderful artwork!
This is a great idea for any sort of DIY artwork: trace a simple graphic onto three canvases, and paint. So much more esthetically pleasing than if you were to just trace and paint onto one canvas. Plus i love the whale idea for a little boy room :)