Colin, what a neat idea!! I agree with the too white also. I have carved a couple mushrooms and here's what I find works the best for me (this is with acrylics but I don't see why you couldn't do the same thing with stains). I paint the mushroom underside a brown color, the top more a tan color, then I take and draw some of the brown, underside color, up through the lighter top color, just around the edges. Makes them look more real to me.
Whatever you decide to do, the concept you have is great! Thanks for sharing them with us!

Deborah