I have tried two image gallery modules (well actually one, the other didn't install but I saw a demo site of it), but they didn't supply what I need.
I need to have a thumbnail of a photo in my website, and when I press it, a full size version of the image is open "above" the website.
There are websites who have this kind of feature, in which it seems like the whole website darkens, there is a loading sign, and then the photo opens above the website.
I also need to have comments bellow the smaller version of the image.
Is there such a module for xoops?
Thank you.

Which gallery modules have you tried?

xcgal and extgal will do most of what you want (extgal can do the "lightbox" effect that you mentioned. Don't forget Gijoe's MyAlbum-P, too.

I have xcgal 2.0.3 (very slightly hacked) running on my site - check your PM for the url.