If there's a young person you know who wants bookplates (or just a way to show the world which books are his or hers)
head over to myhomelibrary.org and see what they've got. (And there's no age check. So the bookplates could be for you, too....) Anyway, if you want a choice of Quentin Blake bookplates, or Raymond Briggs or Posy Simmonds or, well, there are hundreds in different sizes by hundreds of different artists, you click on the thumbnails, print out the bookplate, and stick it into your book.
It's the pet project of British Children's Laureate Anne Fine. Check it out at
http://www.myhomelibrary.org/ (and I found the link to myhomelibrary.org at
http://www.wordpool.co.uk/, a great site dedicated to raising the profile of children's fiction).