In one form or another CircularThing has been around for a while. Now it's our responsive version of DiskThing. Except it doesn't have all the features of DiskThing. It does, however, do one thing really well. It gives you responsive round images that work beautifully on all devices.
Examples are in 4 column fill layout, 250 px thumbnails, with 2px, primary color borders. Idea is to show drop shadow variations. Notably the images are reduced in size with drop shadows, and larger size with inset shadow.