I have no problem if anyone wants to use my work in their own photo-manipulations. I have used other DA members work in several of my pieces, so I'd be a total hypocrite if I wasn't OK with it too. I just ask that you do 2 things:
1. Give me credit. Put a link in the description to my original work.
2. Don't cover or crop out my signature logo. Just because you added a new face or changed some other details doesn't mean its now your original artwork. If you want to add your own name to it too that's fine, just don't cover up mine. And especially don't remove my name and put yours in it's place, thats annoying beyond belief. Obviously if you just use a small piece of one of my deviations and put it in your own work you this isn't an issue. Just credit me and call out which part you used.
I also find it amusing when people use my work, slap a different face or background on it then put one of those big ugly Deviantart watermarks on it. They're so worried about other people using "their" work, but if I did that they'd never be able to use mine in the first place.