We did the frame for my Mom, when we did the 4 generation trip and gave her the photo with the 4 of us in front of the castle.
Last time I used a white fabric tote bag I had bought in one of the Disney Springs (Downtown Disney then) shops. It had artistic drawings of all the princesses and then a completely white backside. With a sharpie all the characters were able to sign the tote and I got the princesses all to sign their dresses on the front! It was a fun different idea and I now have it hanging up in my apartment. The downside is that I am afraid to use this tote ever again because I can't wash it if I do. The upside was that I was using it to carry stuff around in the parks so it had a dual purpose! On this same trip, my one girlfriend got the park map signed and another girlfriend got a Disney storybook signed. Which is what I have started to do now as well (the storybook). Downside to that is that it is heavy!
We've done this.
Also a pillowcase, with a quote from Walt embroidered on it, "It All Started With A Mouse....."
Also a T-Shirt
And I haven't done it myself but I saw someone do this with a pair of white Keds
We use this book and the characters sign on their page. Most are very familiar with them and find their page pretty quickly. I remember when the "Queen" found hers, she marked through the word "Wicked"and said that was wrong! We keep a package of push-top sharpies to make it easier for the characters to use. We have used this book for years and the kids love to read the book while waiting in lines! Our book has become a family heirloom!!! Ha!
We've done this too. It was at least 5, 6 years ago (when Frozen first came out, it was brand new with adding them in it) and the Characters got a huge kick out of reading about themselves.
In addition to these things above, we've done
Regular autograph books bought over the counter
Custom made autograph books (printed pages from designs found here on The Dis)
White wooden initial letter
Large glow in the dark Vinylmation Mickey (back when they still made the thing)
I'm gonna be honest and say that I'm rather glad DGD has outgrown this and we no longer have to come up with ideas I'm flat out of new ones