This one began as a couple of fractals in Apophysis. I opened them in PhotoShop, layered them in screen mode, duplicated, added a gradient to the bottom one, which gave the whole stack a more opaque appearance, played w/ opacities, flattened and embossed for an impasto effect.

Here's how I emboss; I don't use the emboss filter in PhotoShop.
When you've flattened the layers of your painting, make a duplicate file, desaturate, and save as a psd file. Close that one. Take your file you've been working on and go into Texture/Texturizer, click the little arrow that gives a drop-down that says load texture... Navigate to the folder where you saved the desaturated copy and click on it. Set scaling to 100%, and play with the relief slider, usually around 12% is good, sometimes it looks good to check invert. You can watch all that's happening in the preview window and get it the way you want it.