This is a Mordor suggestion for the 2nd Tier Reinforcement of Rhun power specifically towards the cosmetic look of Mumakils/Oliphants
Now to understand my point of view a bit of storytelling is necessary. I was just on a map going around my business slaying all that oppose me and all when I notice that my Mumakil that I sent of randomly had actually managed to survive and go up to level 7. Now back in my BFME 1 days I remembered that Mumakils would gain the cool war paints and barbed wires (purely cosmetic) you can see in the links at lvl 2. Giving the Edain team the benefit of the doubt I told myself they probably upped it to lvl10 which would make sense. Great was my disappointment when not even the glimpse of a tattoo appeared that magnificent Oliphant butt.
So, my suggestion is to give the Oliphants a cosmetic look when they level up like the one in BFME 1 as seen on the links
TL;DR: give the mumakils tattoos
Link for pic (found one that's perfect):
http://matajeux.free.fr/sda/tenebres/autrescreatures/mumak.jpg