Hey guys, recent purchaser. Concept is simple, but it works really well. With so many VR games running at lower resolution for performance reasons, it's nice to be reminded with programs like these just what kind of visual clarity Quest can do. I'm very early in testing this out, but I had a couple suggestions--though one I think you're already on top of.
Lower resolution images don't look as great--pretty expected. But trying the same images doubled in size and bilinearly filtered, the image looks a lot less shimmery. I noticed "Antialiasing and mipmaps to reduce jagged artifacts on edges when zoomed out" as one of your upcoming plans, which I think is getting to the same result.
The other thing I'd like to see, especially if you're going to have a photo viewer mode, is support for stereoscopic images. The most common formats just have two images side by side, sometimes with both images squished to half width. Anyway, I think these images would look pretty nice with the display/zooming/controls you've got here.