Not sure I understand, but that's how I figure it looks more or less:

general /galleries directory for all user directories (albums)

individual /galleries/album directories for individual users.

If /galleries is chmod'd to 555, than nobody (not even you) can add or delete anything to/from that directory. That's what I understood you wanted. To be able to manipulate its contents, you'd have to chmod them to 755 and be the owner, or to 775 and be member of group, or to 777. You may not be able to chmod if you're not the owner of the directory. Owner here always being the first name when you do an ls -l

If /galleries/album directories are chmod'd to 755, then users should be able to write something to them, and to delete something inside them, but not to remove the entire directory /galleries/album, because that's protected one level up. Now, this is on the assumption that users are accessing the directory as owner (or that the first 7 applies to them), which would normally be the case only if they are owned by the user who runs the webserver. If the directories are not owned by the user who runs the webserver, then 775 or 777 might be the correct choice for the subdirectories.

In any case, 555 for /galleries/album directories should not be what you want. After all, your users are supposed to upload files to those directories, aren't they?