New users won't get a blank avatar - they'll either get an auto-generated pixel robot thingie, or it will pull in their twitter picture if they sign up via twitter.
But what about users who existed before the import? Well, for active users, no trouble, they can just go grab their avatar or set up a new one. But there are a lot of old posts with that "missing image" blank avatar now. Here's where it gets interesting. I can either go and manually set up a couple hundred avatars, or I can run a query. The trouble is, I can do php, css, html... but sql is not my strong suit.
So I'm trying to figure out what the proper query is to update null avatars into default avatars (which should auto-generate them a new robot thingie).
Hang on tight! 99% chance that there are no issues at all, but there's a 1% chance that I could break avatars. Which will get sorted out but still, proper notice and such.