Most economical option is whiteboard decals which stick to the wall, and if you're crafty you can cut them to fit inside an oval-shaped picture frame or something like that. Removable and reusable, does not damage wall.
We have white backerboard in our office, and it doesn't properly dry erase at all. Instead of just kind of smudges over the entire area of the board eventually just making it a HUGE mess.
At that point we have to clean it off with commercial cleaning spray and paper towels. It works, but is definitely not ideal.
WhiteyBoard is the only type I've tried, so all decals might have this problem, but I found their product to be pretty awful. Came damaged, didn't stick almost at all. Their customer service is also a absurdly poor, which I'm pretty sure is a problem specific to them - I recommend avoiding.
Agreed, we have this in our offices and it really sucks. We didn't have issues with the whitey boards arriving damaged, but they don't stick very well and tend to slowly peel off the walls. In addition, you can't really erase anything off of them without water or some sort of spray and a paper towel. Erasers don't do jack.
http://www.wallcandyarts.com/shop/category.cfm/whiteboard
All of this stuff is awesome though.