I have been using the alternate Postimage website for a long time including last Friday, but today it's not working for me.
I didn't even know the new site was up until I checked today and saw that, while it exists, nothing is showing up on it. So, does that mean that even images coded "postimg.CC" aren't appearing?
Then we'd have gotten a hot linking warning picture like other sites do. And the main page would tell us that. Plus, it's not hot linking -- PostImages is made specifically to host images and post them.
I think we all just need to wait a day and see what happens.
Maybe they wanted a plural form of "image", just to make it more clear you what kind of site they were.
Maybe they snoozed and loosed their domain name. There are unscrupulous people world wide that try to grab domain names if a company isn't paying attention and keeping them paid up, and them hold them hostages for a large price.