It'd be wonderful if we could pick an earned achievement to display under our names. That's a very popular feature in City of Heroes, and a number of other MMOs as well. That'd add a bit more personalization to our characters, and also make achievements a little more social for the competitive crowd (they'll have something they can show people).
Just an example of how this would work:
If I had the "Zombie" achievement for dying 251 times, I could check a box next to that achievement on my Profile page in order to display it in-game. Then, for Halloween, I could dress up in the zombie mask as a costume. Imagine someone with the "Wood Wacker" title running around in a flannel shirt, a "Darwin Award Winner" dressed in the ape outfit, an "Ace of Om" in one of the monk outfits, a "Knight of the Kingsgard" in one of the armor outfits, etc. The number of possibilities are almost limitless.