We have to distinguish between two cases:

1. You have connected your camera directly to your computer via a USB cable

2. You're accessing a folder on your hard-drive or a flash card in a cardreader

For case 1, the WIA driver of your camera decides which images are to be shown, and which not, WIA-Loader does not have any influence on that. You could try to bypass the WIA driver by putting your camera into 'mass-storage' mode. Most cameras offer such an option in their configuration menu. Then, the camera would receive a drive letter in windows and WIA-Loader could access the pictures that way (see case 2).

Case 2 looks better. Here, WIA-Loader decides which files are to be shown, and not. WIA-Loader has a hard-coded list of file types to display. If your images file extension isn't in this list, the files are not shown. I'm planning to make this list editable by the user, but until then, please contact me by email if you need additions to this list.