Can you tell exactly what species this is from the picture? Well, no, not even if you're a real herpetologist, and not even if I tell you it's a Cope's Gray Tree Frog. You'd have to hear it to be sure whether it was an example of Hyla chrysoscelis or Hyla versicolor, because they're identical in appearance but have different songs. Both kinds actually come in a wide variety of colors, but always have a grayish cast and camouflage pattern.
The linked song mp3s are from the Cope's Gray Tree Frog page of Frogs and Toads Of Georgia, where you can also find a lot more pictures and information about these lovely frogs.
(Oh, and if the suspense is killing you, the one pictured is actually a Hyla chrysoscelis! ;)