Girl Posts Stunning Photo

Obviously not the typical "omg you're so beautiful omg"

I'm not too great at facebook game ... yet. The first thing that comes to mind is to just ignore it, but then she doesn't really know that you're ignoring it because it's Facebook ...

How would/do you respond to these?

You don't want to be one of 40 people commenting on this photo. Use it as a conversation starter on the chat instead.. Remember not to comment on the same things everyome else does, that way you'll stick out.
Use it as an icebreaker and take it from there...
Hope this helps

i usually look at the picture, pick out something in the picture like a plant or a tree, something in the background.

and then, i say "OMG what a beautiful TREE!!!!"

I can understand why Pierrot points out something unusual in the picture and comments on it...I just wonder if maybe that's too transparent. If you say, "OMG what a beautiful tree" that would obviously show you're already thinking of beauty, which she may see as being a thinly-veiled remark about herself. Granted, this is probably still better than flat out saying it, but I think something less obvious may still be a better way to go.