Vshot is an easy to use tool for taking screenshots on GP2X. Unlike other similar tools, it can handle non-standard framebuffer locations and all RGB graphic modes, so it works with most programs out there. It can run in the background and wait for a button press, and uses PNG format (libpng) for it’s output.

http://www.gp32x.com/board/index.php?showtopic=41680&view=findpost&p=602585