I posted the enviros and the "rough" of the girl portrait in a buried sketchbook thread, but I figured it wouldn't be a bad idea to include them pics here.
For the first set of enviros, I spent less than an hour per image. For the second set, I spent a maximum of one hour. The portrait of the lady is painted from photo reference (not a paintover); obviously I added the robot-y stuff, just for fun. The cartoony one is a self portrait I did purely for kicks.