Photographs can be taken in online venues such as Second Life, but you are dealing with a view that is completely sharp – much in the way that a point-and-shoot camera operates. Any depth of field has to be added artificially either in the virtual environment or in post-processing with programs like Photoshop or the GIMP.
Composition and view are still the same, as is the importance of the background. I do however find myself not using the rule of thirds as much, however.
I may post some of my Second Life shots here, and see what folks think of them.