It sounds like you are trying to organize all the pictures you would like to have in a "library" that could be "borrowed" for use by different profiles, as needed.
For that, I would suggest a free space page in which you store all the graphic files you want to use on multiple profiles. You could have more than 1 free space page - for example you could have a free space page for backgrounds, another one for photos, another one for source images, maybe another one for graphic elements like scroll designs or floral designs, etc.
For background and for thumbnail images on a profile, the image file has to be assigned to the page, but that can easily be done. The same place on the image's editing page where you can click the circle to remove the image from a page has a blank box that allows you to type in the ID of a page that you want to add the image to (except that, as I mentioned the strange wording before, it says add the page to the image). The same image file can be added to as many pages as you want. Once the image is added to a profile page, it will show up on the right side of the page and there will be a way to select that image as either background or thumbnail.
Does this help?