Okay, so I managed to figure out, how WordPress publishes images full scale, and updated every one of my image posts (as I said, thankfully not many!) by hand.
Now all of my previous posts from Posterous are okay, and I can have a look, if I can find a theme, which I like.
Incidentally – the WordPress dashboard seems amazing. Lots of options, and I have still not figured out even a quarter of it. I think I will have lots of fun with WordPress.
And don’t even get me started on the web hosting control panel… As I said, I bit off way much more than I can chew.
The experiment continues… now in earnest.