I have been taking one of the CGMA classes the month (Color and Light). It's been really awesome.
I won't bore you with the studies of spheres and materials (although I found the material spheres very helpful- it's a great way of digesting information).
Here are some photo studies from the class however. These were very quick studies, painted very small. The idea was just to capture the color/lighting information rather than all the tiny details. I'm sure I could have noodled on the city forever.
I think in the future it might be more useful to take these studies and extend the scene, or significantly alter the shapes of the elements within. It would really help to digest the information better. The city study ended up pretty lame- I have much more practice painting environments. Yet, I find the repetitive, grid-like, quality of cities interesting.
I also took a break from all my freelance work to do a stylized version of Ged- the same design as last time. I'm probably going to finish it up, I am pretty happy with how his face turned out. Working this way is really fun for me- I like jumping back and forth between this and realism.