While it's not a photograph or anything Oz-related, I really like that it tells a bit of a story. It is a canceled check made out by Judy Garland to the IRS in the amount of $13, 931.13. The check is dated October 14, 1963 and therefore coincides with the time she was appearing on television in The Judy Garland Show.
I like that the check and signature come from a very creative and (I hope) happy time in Garland's life. And this kind of autograph just feels perhaps more real than a signed photo would. It's a peek backstage into a very real and very important moment in Garland's life.