I did some redesigns for the iconic Storm Atronach for the Skyblivion project. This happened to be my favorite atronach because of their thunder and lightning sfx, and, in Skyrim, that stormy animation. There was even interest towards both Skyrim-looking version and Oblivion-looking version, which are very different from each other! So I did one of each, adding some small details associated with rocks - such as embedded fossils, megalithic art, moss - while trying to not make things too different or special for the sake of different or special. So no specific types of rock formations or big fossil pieces, etc... too bad, Iain Stewart.
All in all I had great fun with this, and all those other crazy geology ideas I can still stick them on thunderclasts for fun later! :D But don't hold your breaths :P