Demos for 7th Grade Art Class

I am going to be teaching a class on pastels next week in my son's school; these were test demos I did this morning to see what kind of subject lends itself best to a 15 minute demo and illustrates the points I want to cover. I decided to try a few subjects, including a few based on pop culture, which I thought would hold their interest(no boring apples and pears!). The more detailed portraits take longer to do, and could be dissapointing if you don't get a good likeness. I decided that the figure (Jay Z) was the quickest to do, is easy to replicate, and best illustrates the points I plan to make, so I will likely do that one. Then the kids will have a chance to do their own painting...should be fun!