I get some images from CD's but most of my decoupage is downloaded from various websites or e-mailed to me, although depending on what you're doing with them you will have to check regarding any copyright issue (Most are OK if you're using them for personal use but not commercial). I have a few favourites or a list that I can e-mail you, if you want. Another idea is recycle old pictures, books etc.
Good luck anyway.
Kind regards
Sandra