I activated the metatag plugin. When I view image.php, the html source shows the keywords and description of that image. But when I view the thumbs page, those keywords are not there. I know they depend on the keywords added for that album, but would it not be easier if the keywords were taken from the images inside that album?

Well, it is simply not setup for that since albums can have their own tags.. Sounds like a good idea so feel free to open a ticket so we don't forget it. Will have to wait for 1.4.4. though.

Ok, I've done that