Can you cast spells on them like mage armor, magic fang and the like?
Of course. Why wouldn't you be able to?
I was pretty sure you could. But couldn't really find anything definitive and it was being discussed amongst my players, all who also DM their own games.
Well, the inability to find any restrictions on it is pretty definitive, if you ask me.
Yea, sometimes players think if it doesn't say you CAN, that is also an answer. I was just leaning towards, "doesn't say you can't."