Back in December of 2011, Google changed the way screenshots were handled in the Play Store. Where they used to open in their beautiful, hi-res glory, they have since opened as a tiny version of themselves. It's annoying, especially for tablet screenshots. To circumvent this, you could open the image in a new tab and append h=2000 to the end of the URL, which forced the screenshot to open in its full-size. Of course, this solution was beyond tedious.
After we posted the My Apps GM script last night, Artem mentioned wanting a script that would display high resolution images in the Play Store (and he's not the only one, I've been dying for this since last year, too).