I've used Blender to try and create some desktop wallpapers, they are not perfect and I'm hoping for critic and tips that can help me use Blender in a better way

Here are my finished images:
Click image for larger version. 

Name:	cubes.png 
Views:	29 
Size:	163.1 KB 
ID:	280131Click image for larger version. 

Name:	hexagons.png 
Views:	24 
Size:	585.3 KB 
ID:	280133Click image for larger version. 

Name:	explodingsphere.png 
Views:	16 
Size:	1.06 MB 
ID:	280132