An undo button! I hate when I have a whole bunch of lines and I accidentally draw another line over them and I have to sacrifice a lot of lines just to take out one!
And like what JayJr50 said, you should be able to draw your own ride. :P
Different colors for the scenery lines would be cool too.
I agree with jb701926! When ever I make a little mistake over other lines, and have to erase it, I end up eresing a lot of lines around the one line I want to erase! I don't really get what jayjr50 means by making your own ride though...
I think you should work on the tricks you can do cause flips are ok but maybe if you can add somthing like tail whips or bar spins it will be alot better.