A fun way to build your visual vocabulary is to explore metaphors and clichés. While you should minimize the use of clichés in writing, they frequently show up in speech, and drawing them can make your sketchnotes more visually interesting.
Here’s a sampler of metaphors based on an exercise I did in the Rockstar Scribe class. Some of them didn’t resonate as much with me, so I replaced them with similar metaphors. For example, I don’t really use “against the tide” that much, so I drew a stick figure rolling a boulder up hill. If you play around with these ideas, I’m sure you can come up with even more!