Kardesh had me playing with face and body lights the other night after he taught me how to make one; he showed me that using different shapes and colors can really affect the way your avi looks. (That's one thing I like about K: it's all about the details, and that's how it is for me too.) I love to take screenshots of the avis in SL, so I want to play with this a lot more.
Another thing that I'm learning is GREAT for photos is windlight settings for the water and sky. Torley has a great page on the wiki about them here, and there's a download zipped file of bunches of his own preferred settings there too. I just found that today, so I'll post more pics here as I try them. Meanwhile, here's one I did inworld the other night.