Personally I hope they go the way WoW did by allowing people to write more intricate stuff than just cosmetic changes. Allowing for proper addons will definately make this place a veritable green-house of creativity.
I want to see more serious mapping in Vanguard as well. Not just the parchment-ish birdseye view of WoW maps or the vector linefrenzy of EQ1. Good mapping that you can actually use for finer navigation would be awesome.