How to load/render bitmaps fast?

Hi,

We've created a game designed for tablets (like the Kindle and Nook) which contains many bitmap images (200+ PNGs of around 400x800 pixels each). It's a dress-up game so basically when the user touches a button (let's say the "clothing" button), it makes the clothing movieclip go to its next frame, showing a different png.
The problem is that each time a button is pressed there is around 1 second delay until the movieclip shows the content of the next frame.

My question is what would be the best solution to increase the performance? The images are static by the way, only the movieclips change frame once a button is pressed. I've read a bit on the subject and I don't know what would be the best solution...