When a user uploads a profile image (avatar), ES generates 10 images for that avatar!
I'll break it down:
1. thumbnail
2. featured
3. square
4. large
5. original
6. stock
Then the other four are purely for profile photo only:
7. 32x32 (small)
8. 64x64 (medium)
9. 180x180 (square)
10. 180x180 (large)
I know that most of these images have their purposes, but I do believe we can get rid of a few of these per avatar. When it comes to the avatar we can remove the second 180x180 photo considering that we already have one that is 180x180. In terms of regenerating the image, the stock image is supposed to be in charge of that.

Also we don't need the 64x64 image considering that ES by default displays the tiny profile photo at 30x30 which makes the 32x32 the perfect image for the job.
In terms of non avatars, it appears the square photo (128x128) is only used to display tiny photos on the left side area. The squares are down sized to 36x36 via CSS. So why not have the images use less space? I suppose in the future there might be plans to make that aspect more responsive for bigger screens. 64x64 would do the job pretty well (or 72x72).