At this time, elliptical is not an option, nor is being able to customize activities. However, there were indications a while back that the latter might be an option in the future.
I believe that when this was discussed a while back, a number of folks reported that something like "cross country ski machine" gave a similar calorie burn. You might try to search the message boards to see what others have done; I know this has been brought up before, but it's been a while. (An advanced search will get you further than just typing in the search box on the main page, just an FYI).
If you prefer Classic FitDay, no worries; you can set your profile to have this as the default version for you.
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days