Whoops! I should note that on old devices, the default image viewer is called jpegviewer.app. So, for those devices, the lines in extensions.cfg should look like:
Code:
jpg:@JPEG_image:2:pbimageviewer.app,jpegviewer.app:ICON_JPG
jpeg:@JPEG_image:2:pbimageviewer.app,jpegviewer.app:ICON_JPG
png:@PNG_image:2:pbimageviewer.app,jpegviewer.app:ICON_PNG
bmp:@BMP_image:2:pbimageviewer.app,jpegviewer.app:ICON_BMP
tif:@TIFF_image:2:pbimageviewer.app,jpegviewer.app:ICON_TIFF
tiff:@TIFF_image:2:pbimageviewer.app,jpegviewer.app:ICON_TIFF
I think the picviewer.app application arrived in the firmware version 4 and later devices.