Hi,
I know the thumb size of images is greyed out in the zenpage theme in admin/options/theme with a default size of 95 and you can edit themeoptions.php to change this. But when duplicating the zenpage theme the default greyed out thumb size in admin/options/theme is 100 and editing the duplicate themeoptions.php does not change the default 100 value - strange. I also see in this duplicate the default image size changes from 580 to 595.
I have tried deleting the duplicate and duplicating it again it again but it happens every time.
Thanks
Steve
The Zenpage theme has that option disabled for layout reasons since album thumbs and image thumbs are tied together. The album thumbs are set to a fixed size in this theme.
When you modify it the theme name is different thus no graying out. You will have to modify the theme.