[Polo]

Because of what your describing, I dont think changing the tiles would suit you. instead you should have a fixed ground surface, somthing plain, like straight green, so players dont realise, and then a series of showimages for things such as trees, bushes etc...

These images would wrap around the screen and have varying speeds and directions depending on which way the user is 'flying', and would all be shown clientside. This would (i think) give you the effect you want, and would have the smoothest motion of the suggested methods.

'If' i'm not too busy, I'll probably cook somthing up for you if you ask nicely.