Here's a link to the photo of the day gallery, aka the cover photos
https://www.newschoolers.com/nspg/14.0/Photo-Of-Day?m=621977
as for the resolution of photos, it all depends on the photographer. To make the cover photo a photo must have at least 1000px of resolution, but nothing high res is actually "required." If you want a bigger photo, send the uploader a message! As a photographer myself I don't post high res images on purpose, as some people like to steal them and use them elsewhere without permission