Mockup uses actual items from this month's Picture of the Day feed.
This explores the more 'mosaic'-style model to the gallery view where items aren't cropped and have variable height. I like this for a single column, but I'm not satisfied with how it could work sensible in multi-column.
Clicking/tapping on individual images transitions to a detail screen, with the image stretched, cropped and darkened in the background as we currently do on Android's title/description screen. We can imagine a fancier transition, such as animating the image from its place in the gallery view as it zooms in to the full screen (oooh!) but I didn't mock up the transition yet. ;)
Detail screen contents are based on one of Jared's mockups, using a more compact category view. The items on the detail screen load asynchronously, so be warned they jump around a bit. We'd want to make such things much smoother "for real" of course... we'd also probably use this screen to provide sharing controls, etc.
If the categories, description etc are large, we can easily go beyond a screenfull, and have to scroll this screen. Should the background image stay still during scrolling or should it move a little, parallax-y? (ooooh more visual effects)
Do we want to use the detail screen as the data-entry screen on new uploads as well, or keep them distinct?