The photos below are from a sketchbook that was dedicated to collecting images and drawing ideas for embellishment, eg. beads, etc.
The sketchbook below is dedicated purely to drawing images of trees.
The one below is used for collecting and drawing ideas for work.
I find it useful to also keep all the information I gather at workshops in the one place. I write notes, draw sketches, etc. all in the one sketchbook. See below.