Aktr, more good suggestions there.

Tough a few still miss that interesting extra spice.
Glenn, I read the books as a kid and really loved them, not sure I would still if I read them now. However, there are more then enough wiki´s online made by fans that list all the spells and the effects they had throughout the books. Might be more value for effort returned that way.

While a lot of you are reading this, might as well ask for more specific suggestions. I like the idea of elemental magic even if just for the visuals of wizards clearly linked to an element. However especially with fire I could do with a few more interesting ideas.
A wall of fire is good enough in my opinion as it provides a hazard, which is more tactically interesting then a barrier in my opinion since it offers a gamble, move trough it and get damaged but get on with the show. (or knocking others trough it with another spell?)
You could do a carpet of fire, the fire version of sheets of ice making people dance like they are standing on hot cinders.
But what else? Fireball and stuff like that really isn't all that interesting. I guess a breath of fire spell would be a bit better as it uses a template and thus might hit allies as well as enemies in cramped quarters.
On a different note, I like the idea of wizards taking their time casting, chanting strange words and making occult gestures, so I am considering having an option to have a wizard "charge up" their spells by first spending a turn casting. This would however require many if not all spells to have an extra line or two with their charged up effect.