I wonder if you can improve your skills any more, it is all fine already :)
your decapitations look way better, but maybe you still need to adjust the reflectivity of the surface.

but you can try to do something more complex than just using readily available stuff.

For example, you could try to create dirty looking characters. and for more advanced stuff you can try to do something about stabs and cuts


also, find info about Iray decals. it will be very useful for guro pictures.