as described above; how to do this?
I want to tell a small story with every picture, maybe just one sentence, maybe two...
Thank you very much!

Which theme ?

garland and basic

You mean titles and/or descriptions for images that are used as album thumbnails?

No, I want every single image in an album view with "captions" under it.
I already managed to do so by adding printimagetitle in album.php.
But its only for the title; how do I get the description?

Thing is, I want my images presented with a bit more textual background to them, a bit more like blog post or something.
You may check it out at https://blog.pknr.de
Thank you very much!

Within the [i]next_image()[/i] loop place this call where you want it to appear:
``
You will have to alter the CSS to have it displayed properly.

best you also review the theming tutorial to learn how Zenphoto themes work in general and where to find that next_image loop: http://www.zenphoto.org/news/theming-tutorial/