I have cut those gym type mats and its more of a rough look with the pores. Foam cut skull (not full 3d but partial) - #22 by JeffNash
Also here is some type of foam that others have used => high density urethane foam
Here is a thread on foam that was used for gun cases.
https://discuss.inventables.com/t/something-different-what-i-use-my-xcarve-for/24686/3