I am working on a generalized system that will allow us to unify icon handling: from upload to cropping to serving. I have chosen a test-driven approach and basing it on initial interface proposed by Brett.

Everything is looking good so far, and we can roll it in without BC breaks in 2.2. I need some feedback, preferably some hard evidence on how it integrates with the plugins in the wild. 

Please comment here before it's too late: https://github.com/Elgg/Elgg/pull/9655/files