The skull is solid, like others have said, everything looks intentional and well thought out. There are a few holes that would be visible given your level of detail where nerves and blood vessels would normally move through the bone, but I only think doctors and anatomy nuts would notice the omission.
It has the feel of a classic still life study from southern Europe 1600's, I would love to see just a touch of that high detail rendering on the flower petals, not complete, but similar to the treatment of the skull. The reds really draw the eye and they seem unfinished as a result given the ready comparison to that period.
The materials just underneath the tooth insertion points are difficult to identify, which sadly detracts from the image. The nearness to the skull and the teeth makes me think of intestine for some reason, most likely the death association. More clearly defining those shapes and what they are would help, unless of course you intended to have that effect on the viewer, and if so well done!
Again, great picture, and I do mean it, I would love to see just a bit more detail on the materials that are not the skull, you have a fabulous classically styled piece in the making.
Ahh and one last thing, mess around with the cropping of the image, the square with the bottom of the materials sitting so close to the bottom does not seem to accomplish any effect, its just sort of there.