This shows some problems:
Thumbnails are extremily small, so not very useful. That size thumbnails
are only useful when looking some specific target. But then it would also
be much more useful to see them all at once.
Captions of thumbnails are not shown - would make it much more useful.
Full size images are not very big either, and they are low quality. Even
if they are low quality, they are not very small files. Have you saved
them multible times lossly?
Usually, I advice making full size smaller instead agressive quality
reduction, but in this case size is already small.
Have to scroll that thing all the time, or ignore it...
Originally each gallery looked like the homepage with rows of thumbnails,
sometimes with captions where necessary. This gave a bigger area for the
big images. The trouble with this was IMO that either the viewer was set on
a back/forward journey from picture to picture OR each picture was offered
then the link returned to the thumbnail page. I was sent a css stylesheet
for doing this. If I was setting up for a higher resolution, some of the
problems would not arise, but I work with the assumption that most users
(if there are any) would be on 800 x 600.
I really could do with advice as to whether to go back to the original
style or persist with the thumbnails and images on the same screen.