I went for a theme I have some experience with, to make it easy to come up with lots of concepts.

Theme
Murals & chalkboards

Specific Experience
The essentials for painting murals & chalkboards

List A (simple objects)
-Chalkboard
-Paint markers 
-Brushes, painting cups
-Ladder
-Tape, plastic covers
-Sketches
-Projector 
-Pencils, pencil case
-Overalls, gloves
-Music, speakers
-Cleaning supplies

List B (abstract concepts)
-Bring a tripod and your phone to record the process
-Stay hydrated and use sugar to keep your energy up
-Prepare for the weather with the right clothing and materials
-Step away often to see the mural design or chalkboard in its entirety instead of focusing on the details. 

I have not yet finished all the final spots yet, but here are a few. Set 1:

And Set 2:

I'm still working on consistency across all spot illustrations, but making progress slowly, I hope.  I really enjoyed this class!