In some ways, photography in SL is like photography in RL... because the viewers are people in both cases. For example, the principles of composition still hold.
People are very good at ignoring things. When you look at a scene, you don't take it in all at once; your eyes jump around from place to place. Some things you label important, and those you pay attention to; the rest can for the most part go fish.
When you hand someone a photograph, that photograph becomes the important thing...as a whole. Then the viewer notices the telephone pole appearing to stick out of Aunt Bertha's head, the building peeking out from the left side, the gum wrapper on the ground in front of Uncle Joe.
So... you as a photographer have the job of being the substitute low-level visual processor for your audience. You select what's important, and then make sure the other stuff isn't there, or is all fuzzy so the viewer can still ignore it.
(I've discovered that this can be hard when you're emotionally attached to the subject, because your ability to ignore things works overtime. You have to be able to step back and be professional... and perhaps that's the basis of the old joke about the photographer who had visited some poverty-stricken area and afterwards told a fellow photographer about seeing a truly tragic woman, clearly barely surviving. "What did you give her?" "Oh, 1/120th second, f/2.8.")
You also have to deal with lighting...to an extent. I tried to get a silhouette picture taken at sunset, and couldn't quite manage it; the portions away from the sun were too well lit. Even so, you still can manipulate light sources, and even create objects to serve as fill lighting.
But what about depth of field? In RL, you can take advantage of it to blur unimportant items. Is there anything analogous you can do in SL, aside from hauling out Photoshop or the GIMP after the fact?
I think there'd be interest in some SL photography classes. I know I'd take them!