Alright, I've finally reached the level where people take and use my art without permission, so it's time to lay down some Hard And Fast Rules about using my art.
Many of these have been copied/adapted from my art tumblr FAQ.
GENERAL RULE OF THUMB: WHEN IN DOUBT, ASK FIRST!!!
Q: Can I use your art as an icon/header/etc?
A: For usage on deviantArt, no, you may not. Because deviantArt is a site about posting your own art, using my art as your icon may be misleading to other users, even with credit.
For usage on other sites (such as twitter, tumblr, fb, etc) you may use my art for icons and headers ONLY if you credit me somewhere on your page