Currently, you can send ONE png image temporarily using Send Image to Device from the Simulator.
But it's gone as soon as you press a button, you can't carry it with you to show others or review later, and you can't store multiple images for comparison or presentation purposes.
It would be great if Send Image to Device added to a permanently stored set of images (accessed as a special app or somewhere in Settings maybe). No need for a list UI or file names/dates (though that would be cool)—even just Next/Previous with the D-Pad would be sufficient!
Even deletion could be handled without UI, by connecting to USB as a drive. For that matter, ADDING images could be done the same way instead of through the Simulator. Whatever's easiest to build!
This would really help prototype UIs and test them with different people in different lighting conditions. Thinking about game design issues on-device is a lot different from looking at Photoshop mockups!