First off; "We give all DeviantArt users permission to use our stock in any and all Deviant Prints without restriction."
The conditions we place on the use of our stock are:
1) Please credit us appropriately, with a link back to the stock used, or our main page, if published online. If it is not online, please credit however possible - nothing big, just enough to acknowledge the contribution our work has made.
2) Please send us a link to your Deviation/work so we can see what you've created - either in the comments to the stock photo itself (we may see this) or via Notes (we will definitely see this...eventually).
Additionally,
1) You have our permission to repost works derived from our stock on art and social sites (i.e. RedBubble, Renderosity, personal websites, contests, etc) - we ask only that you still follow the two conditions above (credit and link); if you do not have a DeviantArt account, please send a link to your work to our personal email.
2) If someone requests your artwork for hardcopy publishing (i.e. in a magazine), please email us directly - otherwise we might take too long to get your request. We are usually happy to give you permission and ask only that, once again, you follow the two conditions above - as a side note - we love getting copies of the end result (i.e. a copy of the magazine itself), if possible
Finally, two 'Do Nots':
1) Please do not upload our stock 'as is' or with minor changes (quick filters/colour adjust) to any other sites. We put a lot of time and effort into our stock photos - the reward we get is to see what photocompositors and artists can create with them; As such, our stock is not intended to be used as content in and of itself. This 'Do Not' does not apply to using our stock in free photomanipulation tutorials - which we give permission for.
2) As a general rule, we do not give permission for our stock to be used commercially or for advertising purposes. However, please contact us directly (via the email below) if you have a query regarding commercial use - just because we don't give 'blanket' permission, doesn't mean we won't give it in some circumstances.
The best email to contact us on is vaadas (at) gmail.com
Have fun with our work - we look forward to seeing where you take it!
Cheers Chiaki & Nasrin