Thanks for pointing out the Mail aspect. Major blond moment there! But with the axe I am using the Arcanite BOA. My chest and shoulders are BOA as well and they are transmogrified. So the axe thing is most likely a problem with the application...
The only thing preventing you from mogging mail items, to look like those mail items, is that grey/white items are currently not allowed to be mogged.
Yes, if you are a paladin you can mogg a mail item, but both items (the item you are taking the design from, and the item you are applying the design to) must be mail. I know this because after Plaguing you decided to tell me it was impossible, I went to stormwind, bought a cloth helm on my rogue (who he claims can only mog leather), equipped it then went to the transmogrifier and mogged that cloth helm to look like a blue cloth helm I have in my inventory.
Key point, you must have the item equipped before you use the transmogrifier, otherwise you get the 'items must be the same type' error. Hence why a rogue cannot mog a mail or plate item, because they cannot equip mail or plate. However a paladin, who can equip every type of armor available in the game, has no such restriction.