Last year, I bought a bunch of PlastCraft generic sci-fi terrain: It felt like it needed some rocky terrain to fill out the landscape, so I made a bunch of large red rocks out out of expanding spray foam: The fans are made of thick card and gum container lids, set in a foamcore enclosure. It looks pretty sweet as a full board. It's glossy in this shot because I hadn't sprayed it with Dullcote yet. :) More painted shots can be found here, and the full walkthrough of how I built it is here.
The name of your website continues being accurate. Also, the Minwax polycryllic is used as a component in many wash mixes because it's basically pure acryllic medium, it's also a very strong varnish used even by the plamo/gunpla people (optionally with a coat of matt afterwards to kill the intense gloss shine), you might want to keep it in mind, i need to find a local cheap and abundant substitute.
I will readily admit that my first thought when I saw the rocks for the first time was "A giant red sludge monster!" But after seeing a few, very creative and well done.