I also scrounge scrap pieces of pink and blue extruded foam insulation. I bought a Proxxon Hot Wire Cutter. The terrain I can make with my Proxxon is amazing. Besides, if I re-purpose the waste foam insulation, I am doing my part to be more "Green", keeping it out of landfills, and incinerators, and the air I breathe.
I look at almost everything as potential crafting materials. I recently bought a bottle of Orange Juice: the cap is molded with arches around its sides; it looks like an ancient Egyptian, or Mediterranean cap from a column. Now i need to find more of this brand, so I can get more pillar caps and bases! I've up-cycled oatmeal boxes as the skeleton for a medieval city gate structure: I print PDF cardstock castle wall textures on full-sheet label paper, cut, and apply to the Oatmeal cylinders, and boxes, to make towers and gates, for my fantasy city siege games.
Honestly, my wife now offers me empty bottles, boxes, and other "junk", asking me if I can use it in my terrain making endeavors… I love my wife. Cheers!