Another thing I have noticed using the built in image viewer -
Using gifs/smaller image files does not seem to stall/crash the kindle.
When I was using raw JPEG images the kindle was crashing every 5-10 images.
With rescaled ping images it was crashing every 20 or so, or when I would switch from fullscreen, or rotate, or do any strange manipulations.
I have not yet experienced any crashes when working with these 100-200k 16 color gif images. I don't know if it is their small size or format, or perhaps just blind luck, that makes the image viewer appear to be more friendly with them.
They also load significantly faster than the larger files, but I assume that is because the device isn't working hard to scale them down and dither and such. Also note that you can go to menu, and turn dithering off. You don't need it. The images are already dithered and set to display properly on native kindle display.