Destructibles -- would be cool to have a % chance or a counter that when triggered summons an elite. Each jar broken increases the chance to summon. Like Loiger the Crazed (SP?) who doesn't want you snooping through his books, some demon that loves jars gets summoned in because you have upset him from breaking so much stuff! Typical elite with 4 affixes and drops affected by NV.
Purple named monsters -- if they don't ADD to your valor stack, have them minimally refresh the duration. There are places in game with gaps in elites where maintaining a 5 stack can be tricky.
Enchanting -- love this as a gold sink. Rolling one extra random stat! Could also use gems as a recipe ingredient to load the dice in favor of a particular stat appearing. EDIT: enchant text should be separate attribute and searchable on the AH. I think they should persist between owners or if sold through AH.
Gems -- new gem, diamond. In armor: resist all bonus, helm: movement speed, weapon: life leech