Hi all, I'm not always on DA everyday, and I get requests from people who want to use my work in their own projects. Just in case you want to use something and I haven't gotten back to you about it yet, here's a basic set of "rules".
1. DeviantArt members are granted permission to use any of my works in their own projects. This includes prints and merchandise options on DeviantArt. The only thing I ask, is that your final image be significantly different than my original. Don't just slap a filter on the image and upload it as your own for example.
2. Do NOT sell my images as your own.
3. As long as your image is significantly different than my original, you may sell prints of your image based on mine, outside of DeviantArt as well.
4. Credits are really nice, and I enjoy seeing what others have done with my works. As a courtesy, I politely request that people credit me, link to the original, and send me a link to their finished image. Just a request, I won't hunt you down and murder your family in their sleep if you don't do that.
That's pretty much it. I'm easy-going when it comes to this stuff. As long as you aren't blatantly stealing the images to profit from, it's generally OK.