I like your suggestion of adding samples in the journal to give it texture. I remember doing this as a kid with leaves and cones. I found the book recently and it is still quite good looking. Of course, you would need to treat it for conservation.
I too like Shayna’s journal which could be a very good reference book. I am a Biologist by training and this would bring me back to my biology classes way back when. I am newly retired and was looking to improve on my drawing skills. I think this course will really jump-start the process. It is fun to see what others are doing and learn from their experiences.