A telekinesis option in destruction. Pick up object and throw them at the enemy to damage them, a star wars esque push, pull, grip option. There have been a few mods that kind of had similar options but I was never satisfied with them. Blood magic is another good option. I never found a good amount of dark magic type spells other than conjuration and drain life. And lastly would be addition of nature magic. Druid style stuff would be a cool idea for Valenwood, maybe have the option to pick bolders off the ground and chuck them at the enemy Avatar:TLA style.
Here's the video where they show off the features: http://www.youtube.com/watch?v=DGIgXeGC6Dg
An idea I think would make for an good spell for Conjuration would be probably be listed as either Expert or Master level. It could be a reanimation spell with a twist - upon casting the spell on a corpse, you'd take direct control over the reanimated body's actions, like a puppet master, while you stay behind and can act through the 'puppet'/reanimated target which can last til cancelled or could have a reasonable duration affected by the Necromancy Perk. And of course, allow one to have control over the target's inventory if they're humanoid/had a black soul.
Reanimate and possess a bandit's dead body, pass through undetected while using their friend's corpse, steal their belongings or simply kill them without getting yourself harmed, then let the body collapse without becoming ash piles (something that slightly annoys me about non-Dead Thrall reanimation spells).
Nature spells that are plant based, like vines to pull target towards you or encase them. A rune but it's like a venus fly trap that traps the enemy for x amount of seconds when crossing it. Leaves that can be fired and razor sharp that damage the enemy. Poisonous and paralytic plants etc, so I can make a Bosmer mage that fits in with nature theme more
I'd add hexes/curses and make an entire skill tree dedicated to them.
Burden Hex-slows target to 1/2 speed for x seconds (Novice spell-base cost 20)
Exhaustion Hex-drains x amount of stamina, -100% stamina regeneration (Apprentice spell-base cost 50)
Mind Seal Hex-drains x amount of magic, -100% magic regeneration (Apprentice spell-base cost 55)
Blood Curse-slowly drains enemies health while healing caster for y seconds (Adept level-base cost 125)
Ancient's Curse- -30% enemy health, magic, stamina, and armor rating (Expert spell-base cost 180)
Voodoo Curse-make an enemy an ally for x seconds (Expert spell-base cost 200)
Hex of the Voodoo Master-permanently make an enemy an ally, limited to 2 allies (Master spell-base cost 625)
Dragon's Curse-weakness to magic 25%,weakness to fire/frost/shock 50%, lower armor rating by 25% (Master spell-base cost 700)
The master spells would function similar to runes and places one at the caster's feet.