Yep, i've seen it done. I'd search for it, probably in the DIY section specifically. I've seen a few write ups but I don't recall if it was here, or theplantedtank.net
but essentially you get 100% natural untreated cork, and use aquarium safe silicone to attach it to your back glass wall.
over time it will degrade/decompose, similar to driftwood. but we're talking several years, not weeks or months.
Former advisor and planted tank geek...life's moved on though.