Worthy of a topic of its own, Backgrounds can make a major difference in how it feels to model as well as the practical matter of seeing things properly. Some people probably create muted reference tiles for the background, which could be clever, others may create 3d environments as background and render a set of materials out that would live in those environments. (I've done that with my BASICS series and an out of focus room as background.)
Anyway... I get this started with the one I made as environmental illumination for my apple material. It's simple, but creates a pretty coherence with the mat.
I tried out sanc's 2x2 with color, here's the result left to right top to bottom of blue green red black all 1 pixel each As you can see the colors wrap to the other side and are blended as tho they were vertex colors
Edit: just did a 1x256 for a gradient, and Sculptris loaded it fine
I made a few quick and low-overhead solid-color backgrounds to share. They range from 90%black - through grey as well as some colored versions. They are only 5x5 pixels however Sculptris fills the bg with it so you get a full, solid color background.
If anyone can attach this or tell me how to attach it to my post, so it won't get lost in a delete from my server, I'd appreciate it.