A thought would be to always cache the Gravatar/external image, and test for the existence of it upon load. If it fails, fall back to an auto-generated one (I've used Avity and an Identicon-variant for this before).
I think an option to use another icon system (avity perhaps) could be a nice way to support offline rather than trying to locally cache and deal with remote gravatar images.
Hi,
When in offline mode, avatar url is external, and thus can not be found. Resulting in this:
It would be nice to have a fallback image for this case. Thx!