Backgrounds 'R Me
To the right is a wax resist technique I just discovered. Instructions (with pictures) are here. I'm planning on trying this again with a masked image this weekend (like in the instructions). I'd also like to try it with watercolours and on heavier paper.
A word of warning for the stamp pad neophyte: this technique doesn't work with pigment stamp pads because they're not wet enough.* That's how I produced the colours on these backgrounds: a layer of pigment ink that didn't show the crinkle followed by a layer of dye ink, which does react to the wax.
ETA: Watercolours work but your brush needs to be very, very dry. Toothy paper is not very good for this technique because the texture minimises the impact of the melted wax.
*Suggestion to break out the dye stamp pads was made by Ptichka.