You could not use the "snap" to display photo in MameWah ?
Just a guess i don' t MameWah , but if you create a layout displaying a Snap in full screen. And point a "snap" folder to your photo directory and may be add the photo list as gamelist?
In Atomic you can do that in that way. Just create a layout which display only a "Marquee List" in fullscreen. Set the number of item displayed for the MArquee List to 1 . Then make point the "marquee folder" to your photo directory , and make point the ROM folder to your photo directory too.
Set the ROM extension to "JPG" (for instance) and Snap extension to "JPG" too. then you should be able to brownse your photo in fullscreen on your cab.
May be Minwah , using the same kind of trick it could be possible on MameWah?