You can practically go anywhere for great wallpaper. Most people don't do that and used family photos or cars. Basically, a personal photo that is commonly used for mobile devices. Or simply search google mobile wallpaper.
Yep I am aware of the Galaxy themes store. But there are dedicated wallpaper sites, but most of them have the orientation (resolution) of iphone, or S series, etc (slab phones), but the inner screen of the fold is different aspect ratio. For instance this picture is 2304 x 1440 where the Fold would be 1812 x 2176 https://wallpapercave.com/w/Kfy6T0k I just thought some people here would know of other dedicated websites for wallpapers with the Fold aspect ratio. My bad for not being more precise in my original post explaining.