Slideshow wallpaper using files in hidden folder

I've got some nice photos in one folder and their specially cropped versions in another hidden folder (the name starts with a dot). How can I use the cropped photos from the hidden folder for a wallpaper slideshow? No matter what app I try to use, it doesn't allow me to use the hidden photos. I don't want to make them visible; I don't want duplicated photos in my gallery app. Is there any way / app that would allow me to use the hidden photos for a wallpaper slideshow without having to make them visible in my gallery app?