pyMap is a simple map viewer using python, its basically just a glorified image viewer with scrolling support and the ability to switch through images.
You'll need the gp2x python implementation on your sd card for this to run.
Some NYC Subway maps have been included as a demo.
I've been using png files with this viewer, so thats all I know works 100%, though pygame should have support for plenty more. I have no sanity checks for incoming files though, so don't put anything which isn't an image file in the /maps/ dir or it might crash. Huge files (i'm talking more than 2000x2000 here) can also crash it.
Use the stick to scroll the map, B button to toggle through the scroll speeds, and L and R to switch through images located in /pymap/maps/ (by default)