Here are some pictures of the window on the ceiling of the landing in my flat. I think it's beautiful, it's so grimy but I never want them to be cleaned. I love little features like this, which you really don't get in modern flats.
The pictures don't really do it justice- as with the flash you can't see how grubby they are, and without it's a bit blurry, but you get the idea.
Also, the date is wrong on the pictures... I'm trying to work out how to get rid of it completely.