Despite the picture being rather grainy (inevitably from the scanning), you can still get the basic jist of it.

It shows Nova standing on a metal walkway of some kind, and in front of her appear to be some sort of firing points, with a marine in each. Interestingly, this is one of the first shots that shows an outside environment, and although the caption reads 'A Zerg rush threatens to overrun Mar Sara', I have reservations about whether this level is actually set on Mar Sara. Firstly, we know that Mar Sara was completely sterilised by the Protoss at the beginning of StarCraft, and we also know that Ghost is set a little while after the events in BW. So either this is some sort of 'flashback mission' or it is not Mar Sara. The other, minor possibilities are that this is set right at the beginning of the game, or that Mar Sara has, for some reason, been re-colonised by the Terrans.

This is also the first screenshot to show Mineral Crystals, and they're looking quite nice, with some good transparency effects.

The radar shows only one pie-wedge (as I call them), which is facing directly upwards. This seems to support the idea that Nova isn't represented on the radar, instead being in the middle of the bottom edge of the radar.

Looking around the rest of the picture, there appears to be a red 'splat' effect just to the left of the marine on the left of Nova. This is most likely a Zergling that has just been eviscerated by the Marine's fire, since there are a few Zerglings running along under the rock arch.

In the background, there seem to be a few rock pillars, and in the far distance is an explosion from something, possibly Siege Tanks, or some sort of Orbital Bombardment?

Nova herself looks in perfectly good health, with full ammo and her cloaking ability selected.

Finally, in the back of the shot is a ledge, and what appears to be a crate on top. This part of the photo has confused me, since it appears too large to be an ammo crate, but in a bit of a stupid place to be a crate of supplies.

Well, I think I got a bit carried away... I wrote a fair few words. That's the end of boggy's first screenshot analysis.