Todd added this one- Flickr is a photo sharing site that has attracted many semi-professional and professional photographers as a place to share the work they do. The free version allows you to share and organize many images as assign various types of creative common license to them. It is a place to get noticed and to notice others. Like many of the more popular sites like Pixabay or Unsplash, it has an amazing amount to images.
Flickr could be used to share images of a class trip or a series of graphs created by students. Because it allows you to organize the images into galleries it give teachers and students to option to curate specific content. Flickr groups are, "Flickr groups are a great way to share photos, post comments, and hold discussions around a common theme."
Below is our class group that you can join and add photos to here. You'll need to create an account if you don't aready have one.