My personal opinion is that it is much more fair to photographers to have a small byline directly under the picture, or at the bottom of the page. Unfortunately that is up to the local community to decide. I believe the Norwegian Wikipedia does credit in a byline.
Doing that would give the image contributors much more prominant attribution than the text contributors which I don't think think is very fair, especially as frankly many of the pictures are just decoration with the real information being in the text.