BTW, I noticed in Novi Sad - in shop windows and in a glass display in the center - panels with photos of what we figured were high school graduates. Can you tell me what is this all about?
That's most likely just it - photos of high school graduates, or as it is called here, maturanti.
If I'm not wrong, it's some sort of tradition going several decades back, if not more. When maturanti graduate high school there are big photo sessions etc. and in the vein of that tradition, photos are displayed in windows of various shops. To be honest, I'm not sure why is that done so and how it originally began, but I assume that during post-WW2 period, after everything country had gone through, having a new generation of young men and women graduate high school was a sort of festive event, something worth celebrating. So pictures were placed like that in various places, most prominently shop windows.
It's not an ever-present phenomenon in the whole country though - there wasn't anything like that when I graduated - even though, IIRC, our school director (who is very old) expressed her wishes to have a comeback of that picture displaying, but it didn't happen. We had photo sessions though. Ugh. Waste of time.
I think only some schools celebrate the graduation in that sort of way, and mainly schools from "up north" i.e. Belgrade, Novi Sad etc.
In any case, how did you like the beer? And more importantly, how was the concert?