One is a site from the University of Washington called the Great Wall that has text accessible to Intermediate English Language Learners and some nice photos. It’s part of an impressive China project they’ve developed.
I really like this other site. It’s from an organization called The China Guide, and it’s a cool Virtual Tour of The Great Wall. It gives a 360 degree tour and you can click on “hot spots” to move throughout the wall. The same site has good photos of other Chinese landmarks as well.