Ive looked into the ViewFlipper, but defining 40 different views in one XML doc just doesn't seem like a bright idea. I know there has to be a better way, I just don't know how. I have spent some time trying to find a answer with no good answer so far.
I have used the Gallery widget (admittedly quite heavily modified) to display 200 fullscreen images in an image viewer for a client.
Alternatively you could use a ViewAimator with either 2 (in this case ViewFlipper) or 3 views (3 if you want to preload both the next and previous images). If you go for this approach then Laurence beat me to suggesting this idea ;) However I'd add that you would want to extend the ViewAnimator/ViewFlipper class to allow it to accept some type of Adapter.