I'd say the one on the right is better design wise. Things I would change for starters: Up contrast a ton, darker outlines for the darkest parts, and remove the dotted lines separating the teeth from the rest of the structure. If you feel they need to be separated, separate them one at a time with solid outlines, perhaps with a lighter shade than the outmost shades. Make the rings around the spikes gold or silver or ebony.
When I think "macabre or horror" art I think of intricate interlacing patterns personally, and lots of darker, muted shades with bright flourishes of black and red and white.
Edit: Oh, and drop the white background unless this art is going to be displayed on solid white. Colors are relative.