Yes and No. You can use the same picture as many times as you would like for the same pet. However, you cannot use the same picture for multiple pets on the same account or on other accounts. Sorry, but changing the color or background wouldn't' be enough to be able to use it for different pets. Also, if your Neopet has won the Beauty Contest with an image, you can no longer enter that image into the contest for any pet on any account. Even if you adopt out that pet, the image can no longer be used!