Horticultural capillary matting will wick, but I think not as far as one would think (vertically, anyway) if memory serves. I had the idea a few years ago to try a piece of it with the bottom edge in water hanging in front of a small fan to try to increase humidity on a plant stand shelf, but it didn't work in that it didn't wick far enough to stay wet in front of the air current. Maybe if dipped on the upper edge in a water reservoir and allowed to seep downwards, that would wick further due to gravity, which I believe is how folks get Hygrolon to stay damp over greater distances. Anyway, I keep meaning to try capillary matting as a background in a small terrarium. Capillary matting is sold online, often by African Violet and/or greenhouse supply companies, and looks/feels like felt, though I don't recall what material it's made out of.
Kind of the opposite of the OP's request (something non-wicking I assumed), but there it is.
I have found Matala pretty easy to cut to size, at least, which might not be the case for other alternatives.