It's not possible to use Leiothrix Skin Extension with XWiki 7.4 (I suppose it's
valid for all 7.x versions). The extension can be installed, but the pages are
corrupted and functionality like main drop-down menu is not available.
I am aware this skin was not created (I guess) by XWiki dev team, but it's the
only prepared skin suitable to be used as public web and is used in Public
Website Flavor proposal as its basis.
It would be nice to derive this skin to a new one with same or smilar
functionality that will be compatible with version 7 branch, especially if 7.4
has been discussed as a candidate for new LTS version.