Kevin
i have a question are you planning to do this for a personal item or do you have aspiration to sell this work? because there are other things to consider, like image owners copyrights, and other things. yes some people might say that if you change it enough (50%) you dont have to get permission, but isnt true at all, and a violation of a copyright can be very expensive (more then the work is worth).
My suggestion is that if you find aimage that you like and want to use is that you get in contact with the orginal creator and see if they will let you use it, or license it to you for the work (it may cost some money but its dependent on the photographer)
i hate to put it this way but alot of photographers amatuerand pros alike are very protective of there images, as with the internet most people think that they can take a image off the internet and do what ever they want without asking, which inturns can cost that person a great deal.
if you need any morehelp on this subject please feel free to ask them here or PM me and i will help you any way you can
Dan White
aka
Scubatooth