Zombies eat brains.
Not a direct answer to your plea, but you should be able to find posts that link to your old domain with an advanced Google search. I tested it out by searching for links to imgur.com here on meta and it turns up image links too.
At least using that you should be able to update your old posts to point to your new domain.
I think building their own image server would be a waste of valuable developer time and resources. But easy integration with something like yfrog would probably pay off.