From inDev Software:
GrxView 3 is a full-featured image viewer for your Palm. It features multiple native image formats support (JPEG, GIF, PNG, BMP, WBMP and PCX), file manager capabilities, image zooming/panning and flexible plugin-based images decoding.
You do not need to convert images: GrxView reads them in a native format directly from the memory card, so you can review pictures taken with your digital camera right away.
Also GrxView 3 supports Exchange Manager, which allows you to receive and view images of all supported formats from Bluetooth, IR connections and email attachments (tested with SnapperMail and VersaMail).