In Admin Settings you can specify different avatar sizes. On our altered Discourse profiles, I set the height and width of the image to be 220px. The image looks a bit pixelated.
If I stick 220 in avatar sizes, will this help? 
I think it should work with sizes < 1000.
Thanks for that info. So if I put in 220 for example, do I need to run anything to change images on the site? Or will it only work for all future users.
Also, wondering about this:
For avatars uploaded to Discourse, it says the natural size is 240 x 240, but if you put the width and height to this, it doesn’t look as crisp.
This is just my old gravatar being bad.
Ok, so technically, assuming everything is working well, I can set a new avatar size and uploaded images will be stored in that size as well.