I'll need photos that are at least 1000 pixels on the shortest side. I won't actually be inserting them into the site that large, but it gives me flexibility when choosing where and how to lay it out into the design. I can always size down a photo, but will lose quality if I try to size it up.
Your gallery photos can be however big you want them to be. However, I recommend optimizing them for the web at 60-70% compression before trying to upload them through your VedaCMS website manager.