I recently found this free viewer (XnView) when looking for a way to view TGA files on my x50v. The most common application that uses TGA files that I'm aware of is iLauncher. There may be others. I personally use it to browse for TGA images I have stored on my Axim to use as iLauncher icons.
XnView is VERY similar to Resco Photo Viewer. The interface appears to operate pretty much the same as Resco, although the GUI doesn't appear as polished. See screenshot attached to this message below.
XnView will read JPG/JFIF, GIF, BMP, PNG, 2BP, TIF, PCX, PBM, PGM, PPM, PNM, XBM, XPM, TGA and it will convert to and write JPG, GIF, BMP, PNG
Another WONDERFUL perk is that it has a screen capture utility built in that will allow you to delay your screenshot for a few seconds (1, 5, 10, or 15) to allow you to switch to another app to capture. XnView's screen capture doesn't make you save in BMP format, either; you can also save in JPEG (custom compression ratios!), PNG and GIF.
If you browse around their site, you'll see they have a desktop version of the software that is also free. It doesn't have any interaction with your WM device, but it does a pretty decent job at image browsing and conversion.
When you go to download the software you will need to provide a name and valid e-mail address. They will then send you a download link for your copy of XnView Pocket. The desktop version doesn't require you to submit this info.
XnView can be found at
http://www.xnview.fr/site_uk/Pocket_uk/