I second the character (or even ride) sketch that Mary Jo suggested. Off the Page in DCA has the characters in a book that she can choose from and have them customize it (dates, names, etc.). Disneyana has the characters as well as pictures of the rides that the artists can do. I absolutely love commissioning the artists to do one sketch for me when I go. I have a couple from Disneyana that are incredibly special (at least to me). One is of Mickey in the stretching portrait room in the HM. I spoke with the artist who had come up with the design and she told me that she actually won their competition with it (apparently all of the artists have a competition every year where they come up with a new design to be put out). The other one I love shows just Mickey, dressed up in his Halloween costumes under regular light. When you shine a black light on it, the Hatbox Ghost appears behind Mickey like he is stalking him. In talking with the artist who drew that one, she said that they were planning on doing more drawings with the black light pencils from now on. Apparently, their former boss had nixed the idea when they had originally suggested (she had no idea why) and now their new boss loves it and is encouraging them to use the black light pencils in more of their artwork.
It's been really special for me to chat with the artists who spend their time doing this. They really seem to enjoy it and love talking with people who appreciate their artwork. The artists at Disneyana seem to have more time to chat with you than the ones at Off the Page although I suspect that is because the ones in DCA are just hammered trying to get their commissions done and people don't really seem to know about the ones in DL.