If you just want a type of shape of mickey or most any of the other characters you can try any scrapbooking store. They sell all kinds of things like that. I am not sure that is what you are looking for or not. Hope that helped....
I have found TONS of Disney scrapbooking materials at Michael's. . .they have TONS of Disney stickers that would be perfect for placing in your autograph book!
Well, shoot, I wanted to make an autograph book for my DD and forgot all about it. Hope I can squeeze it in in the next 50 days! Good luck finding what you need.
A google image search would help you find tons of images. I'm not sure if you want computer images or hard images (such as stickers, etc...) Good luck!