Very nice work, and not done in a high-value white which is more pleasing to the eye and more realistic. A TOUCH of raw umber migght help w/ shadows - I agree the need bit of a punch. But, no matter, and excellent piece well done.
Any lettering would be on the side facing the figure, not the side facing the viewer, so your gothic letting should be reversed!!!

I'd put in a few shadowy squiggles to SUGGEST letters on the other side - or skip the whole thing.