New on Archive.org, “Cthulhu from Lovecraft’s sketch” in .STL 3D model form, by Perry Engel. Under Creative Commons Non-Commercial. My render…

Also a “Lovecraft bust” by Philipp Franck. Again as a 3D-printable .STL file. The eyes lack detail, but you might do something with it if you can get it into ZBrush.

Archive.org has newly uploaded a million such Thingiverse items. Mostly .STL, mostly under some form of Creative Commons. At present the thingiverse.com site is unreachable.