Well, I can't do a 3DSM tutorial because it's all photoshop ... and for ideas on how it's done go to
http://www.artofgregmartin.com and read his planet tutorial and his "Riven" Walkthru.
I'll see what I can do about my own tutorial, but It was really 5 hours of ... hmmm lets try this, and hmmm what does this tool do (Because photoshop is the worlds most annoying program (next to MAX anyway

)