Humanity and Oxygen themes result in missing icons

[Valtam]

I've also noticed that in the stock LL, there are themes and icon sets in the respective directories that DON'T show up as choices in Appearance. I'm guessing that it may be because they're not XFCE compatible?

Possibly, either way, xfce-look.org should always be your first (and I would recommend only) port of call. XFCE stuff for XFCE system

In the quest to make things in LL as 'goof-proof' as possible, as far as ''don't hit 'Restore System Configuration'" goes, one of the projects to possibly consider to act on in the future is to go into the source code for Alacarte, and to 'grey out' or remove that selection. However, any updates to Alacarte would most likely require the new mods to be re-applied...

That's not something we would tackle, it's to much maintenance.