Would need more info. Just redownloaded it from here and retested it - works as per the screenshots on the standard game (2.1 Christmas). Didn't try compressed, but should work on it too provided you overwrite the existing file.
If it's not doing anything at all then I'd suspect the screens.rpy hasn't been installed correctly in the game folder? Should look like this:
At the very least it should change the save slot text colours & date-time stamp format without you doing anything. When you click on a slot to save that input prompt should appear in the bottom left.
This was answered some pages back, that gallery item can't be unlocked in normal gameplay: