I've done Mickey (several times), Minnie, Sebastian, Pooh, Chip, Eeyore, Ariel, Dumbo, Simba, Genie, Peter Pan, a castle snow globe, one of the Country Bears, Zazu, Pluto, and Tigger. That probably isn't all, but it's all I can think of at the moment.
From my experience, people are harder. The animals are a little more forgiving and faces are simpler to copy. Human hands are hard for me, too.
What princess are you thinking of? I might have something I could scan for you, once I learn how to scan with my new scanner. LOL!
Have you looked in picture books as well as coloring books? Maybe look for coloring pages on-line? You can always change the size of the picture you choose. I've also been known to put a flower or something appropriate in a hand, to make it easier to copy and tie it to my page.