Painting my "forest" sketch last Saturday made so happy, that I decided to paint another little forest on my sketchbook cover, which had still been all bare so far. Sketchbook covers really can't be left bare, I think, but sometimes, it takes a while until the right design/picture emerges.
I love looking through my old sketchbooks. Some of the things in there, I've quite forgotten I ever did over the years. Others, I remember very well. There are sketches for paintings I did, or not, techniques, colour samples, and more. The cover of each book also tells the story of my styles and tastes at the time I started it.