Making a photo collection look interesting automatically is actually really straightforward. I think anyone who spends serious time attacking this problem will arrive at a solution.

Use the EXIF timestamp of when each photo was taken. Make a web page for each month, and group photos together by day to make it easy to skim through. Limit the number of photos shown on this page for any given day (put the rest on their own page) and you've automatically got variety. With those two simple organizational steps, viewers of the photo collection are set up for success in quickly finding photos that interest them, assuming there are some.