I've also found a use for disused paint palettes. When I hold a workshop that requires the students to use paint, I give them a white, soft plastic disposable plate. When I was cleaning up after one of my workshops I was amazed at some of the colour combinations on the plates. I decided to cut out some shapes, flowers, hearts, circles etc then stitched them onto one of my fabric journal pages. I've been using them ever since. They make great tabs for the sides of the pages too.
Here's an example.
The disused palettes.
The cut out flower.
The flower stitched onto a journal page.
I rather like the look of the next palette showing through the cut out.
I will probably stitch these two together for another effect.