Watercolor Painting with Plastic Wrap, Bubble Wrap, and Waxed Paper

Here is an interesting technique for working with watercolor.  The artist doesn't show all of the process, but after she removes the masking fluid from the dry paintings, she fills in the flowers with more paint.  However, you could leave whatever designs you make with the masking fluid as silhouettes.

Card makers, you could skip the masking fluid part entirely and make the interesting backgrounds for card making purposes.  It appears to me that you would need real watercolor paper of a decent weight to do this, though.  Not just any paper would work.