As giopet has replied on the openatv thread.
They are experimental images, (as you are both fully aware), so any issues raise them on openatv github 7.0 branch.
The skinned menu not showing is probably an unnecessary name change or a broken bit of code with is preventing the screen name="menu_mainmenu" from being skinned.
(I am not changing anything in my skins for that - as it would break every other image other than that one)
name 'selection' is not defined, is something they have broke and not fixable by a skin author.