The technique and lines are great, but, in MHO, the shadows near the face are too dark that even opaque the trace lines of the face itself, the shadow of the back and hair lines also dissapear; the skin tone could be a little less dark so the tatto work can also be seen since it also gets diminished by the dark shadows and skin tone. The squid/octopus tentacle looks like a "tail" or accesory one cannot realize if its hanging from the bottocks or touching her derriere (due once again the black shadow surrouding the main character) Just my $0.02, besides that the idea and line art are just fantastic!.
I think you have a great shape set up here, about my only thought would have been to shade out the shadows a little smoother, Shadows are usually never that defined. Might be me, but her Right Eye & face looks just out of portion to the rest of her face. other than those points I really like what you have produced here