What a coincidence! When I was working on my card for the Monday Challenge, I made another background using the Ken Oliver Color Burst pigments and was trying to come up with something that would work with all the "Violet", "Ultramarine Blue" and "Pthalo Green" that were overwhelming the card front (I had issues with that Violet --- very hard to control the spritz of powder and I got WAY too much on the card.). It wouldn't work with a "normal" image or sentiment and so I painted a color wash of blue, using the Distress Marker "Mermaid Lagoon" and a detail water brush over the top of the card to try to tone the splatter effect down a little. Once dry, the Color Burst powders seem to be pretty resistant to reactivation, although where there was “too much” powder applied, it did reactivate and streak when I brushed my watercolor wash over the top.
I then searched my stamps for something that was as random as the background. I stumbled upon a stamp I hadn''t used yet! It was "On the Spot" by Stampin' Up! (circa 2004). So I mounted it (yes, it had sat in the drawer since 2004, never even opened, let alone mounted!) and stamped the background with Versamark and then heat-embossed with Commotion Clear Tops' “Bright Mediterranean Blue” (161327). I stamped a sentiment from another Stampin' Up! set ( "So Very", circa 2007) in Archival "Jet Black" and re-inked the word "So" with a Signo Uniball white pen (the "Jet Black" couldn't compete with the purple blotch! Even the Signo pen couldn't as it did pick up a faint purple tint from the background!).