Ophelia Drowns is a blog well worth reading... and beautiful to look at, too. It would be darned near perfect if the sound clip defaulted to not playing.
(At this point you can just feel the "But..." coming. Why is it that we are so much more motivated to speak up to disagree or complain?)
I have to differ a bit with the recommendations in the entry "Picture Perfect," though. Yes, definitely turn on all the graphics knobs you can afford to turn on, and run those detail sliders all the way up... but facing full into the sunrise with a face light on makes your avatar look like a cutout paper doll, wiping out essentially all depth cues. Professional portraits aren't taken with the flash unit pointing directly at the subject for exactly that reason. That "full body 5 o'clock shadow" at least shows that the avatar isn't flat.
For example, this is taken on Apollo, full face into the sunrise... and darn, I wish I could remember whether I had the face light turned on.
Here, OTOH, the subject is facing north at sunrise. Now, whatever else one might say, the subject is clearly not a cutout... and SL being what it is, nasolabial folds and other wrinkles are of no concern to us!
Not to say face lights don't have a use; they are great as fill lighting. Silhouettes are great, but the only way I know of to get something like them in SL is a pseudo-silhouette you get if you ask the snapshot to show distance rather than color. Barring that, you need the face light for something like this photo, with the subject facing away from the sun:
...and often they're needed if you're shooting at midnight. (The face light is a special case of an invisible light source. If you're really into photography, you will want to roll your own and position them where you wish; Torley Linden has a great video with many photography hints, the easy creation of fill lights being just one of the techniques shown.)
Experiment, and choose what looks good to you. My preference for depth cues is just that, and your mileage may vary.
UPDATE: Duh! If I knew anything about art, then I'd have known that what I spent so much time talking around is chiaroscuro. Do you like yours subtle (Ms. Ophelia's "after" picture does have very slight shading indicating depth) or more blatant? Both have their places.