Once upon a time, I cut out (with scissors!) photos of my characters, along with symbols that reminded me of them. (Track shoes, a broken heart, a winding road, musical notes.)
This process involved plenty of scotch tape and way too much printer ink. If I rethought my characters, I had to rip everything up and start over.
But one day, I discovered Pinterest! It's an online bulletin board where I can search photos, paste and drag them to "secret" boards only I can see, and delete the images as needed. I love this visual collage. It's fun to see how things change over the course of many revisions. Here is a board I created. (I changed it to a public board so you can see it!) https://www.pinterest.com/stefwass/wip/
I also use Pinterest to keep track of my favorite middle grade books. You can check it out here: https://www.pinterest.com/stefwass/books-worth-reading/
For me, Pinterest has definitely helped my writing.
Such a great tool!