Hello,
is it possible to use different themes with different pictures and different user-logins with only one single installation. If I need one installation for every gallery is there any other option to handle it, because this would be a lot of webspace?

Thanks for your help.

We have the so called "album theme" feature that lets you assign special themes to certain toplevel albums (inherited by subalbums). Also I suggest to look at the user guide about the user rights management.

Thanks, I will look if it works for me.

You might need to do some custom coding depending of what you want to do so I suggest to read the theming tutorial as well.