I feel that I really need to work on my rendering skills. I scanned in a sketch and then colored over it in photoshop using a wacom on a 1024x768 photoshop document. What can I do here to improve my selse of detailing, texturing, and lighting? Should I be working at a higher resolution?
I'd suggest going to at least 3000 pixels in width while working on it. You can make it smaller when you're done.
Generally with warm saturated light comes cool desaturated shadows.
keep it up.