Duplicating Goblins (and encouraging war mounts)

All right. So I'm competent enough at DF (or know enough sneaky tricks) that a vanilla game doesn't "do it" for me on the warfare front. While I've used and enjoyed them, neither am I a huge fan of the mods that add Illithids and Snakemen and War Mammoths to supplement the occasional goblin raid. Personally, I'd prefer to simply have more goblins.

... Now, I understand that it really shouldn't be difficult to duplicate goblins and have what is essentially a second (or third or fourth!) tribe. But I've had some concerned that I'm not doing it right, if only aesthetic, because the new faux-goblins do not make use of the graphical tiles. Perhaps it's a silly thing for me to worry about, but it makes me sad to see mobs of "g" swarming the countryside when everything else looks so lovely. Is there a way to make the new goblins use the regular goblins?

And, if anyone would be so kind: what is the relationship between a civilization and its mounts? I am well aware of the [mount] tag and assume it validates their availability to be used in a siege, but is there details on it that I missed on the Wiki? I had a mod that had a race of dark elves that always assaulted my fortresses with giant moose and I thought it might be fun to personalize the mounts for various factions, if that were a possibility.

Cheers.