Glad you like them

Well, the ones with the geometric shapes don't take long, the nebula take a bit more time to do because I'm playing with Volumetrics, which have a mind of their own (you're basically working with procedural transparencies that are caclulated on an x, y
and z value, the objects get denser or more transparent in true 3D, not just a 3D shell).
The really hard stuff is the stuff I'm making models for, which obviously takes longer, but one idea I had was for an alchemists lab, that's going to take just about every feature the renderer has, displacement mapping, subsurface scattering, light-emitting objects and liquids, several types of volumetrics etc, I'm hoping to set a scene up to render while I'm away on holiday for a week in August, since it's probably going to take 2-3 days to render at desktop size

In comparison, the second Desktop picture up there took about 1 hour to design and about 2 hours to render.