Speak of the devil and he shall appear!
Hi Crin. I did make some skull walls. I made skull molds using Smooth-On products, but you can use store bought foam skulls. If you look at my skull wall picture you'll notice the the profile skulls and the bones are just K-mart props. I cut the store bought skulls in half so I would have to profile skulls to make them stretch a little further.
I used OSB panels. They are heavy, but less smooth so the texture helped a little bit. Plus, they are among the cheapest panels you can get. I slapped the panels on both sides of a frame built with 2x3s. I cut some random holes in the panels on the skull side to give it some depth instead of a flat wall. I used Great Stuff, lots of it, to add to the wall texture and adhere the skulls and bones. I used pink and blue foam scraps to fill in the gaps around the borders of the holes I cut. I need to find some construcion pictures, but here's what 3 of the panels looked like: