Go to this post on page 7 of this thread for the details:
I have started a poll over on the Kindle Boards and would appreciate your input. I'd like to have lots of votes so that when I contact Amazon I can have a lot of support behind me. I can't do a formal poll here on the Amazon boards, so you can either post your response here or go to the KindleBoards and vote there. The poll is located at: http://www.kindleboards.com/index.php/top
Personally, my 1st choice would be a user-accessible folder on the Kindle that I could put images in to be used as screensavers.
My 2nd choice would be an "app" of some sort, even for a fee, that would allow me to control my screensavers.
My last choice, if Amazon is intent on not allowing user-created images as screensavers, would be to allow Kindle users to choose from a list of available screensavers. Checkboxes or something similar, so I can just quit seeing the images I don't like.