Marqueed is similar to Thinglink but allows for a discussion on hotspots in an image.
According to Larry Ferlazzo:
First, it lets you drag-and-drop images from the Web or from your computer.
Second, you can draw as well as type your annotations.
Third, you can create collections of your annotated photos that can be made public or private.
Fourth, and most importantly, you can have multiple people annotate the photos. In other words, multiple students can collaborate in annotating photos.
Here is one I made...
Here’s a short video about how it works.