Phew, what a SB! When you say quickies, what amount of time are you referring to?
for example this one : http://mv.cgcommunity.com/images/wakeup.jpg
your ability to render environments quickly is stunning and you have a good eye for
mood and atmosphere as well as colors.
If I were to give you crits, it would mostly be about tackling characters and figures.
Do you find the time to draw from life a lot? If you were to translate your environment
skills and quality to your figures, I think you would certainly rise to new levels.
Just my humble opinion
Hope to see more soon.