SWF 13+ (Flash Player 11, AIR 3) the practical limit is the amount of memory available. (The theoretical limit to width or height is the largest positive integer — divided by 20 to allow for twips, but you will hit memory limits long before reaching this size.)
SWF 10 (Flash Player 10, AIR 1.5) the maximum size for a BitmapData object is 8,191 pixels in width or height, and the total number of pixels cannot exceed 16,777,215 pixels. (So, if a BitmapData object is 8,191 pixels wide, it can only be 2,048 pixels high.)
SWF 9 (Flash Player 9, AIR 1.1) the limitation is 2,880 pixels in height and 2,880 pixels in width. If you specify a width or height value that is greater than 2880, a new instance is not created.

Flash Player 11 is very good 🙂
Flash Player 10 need alchemy 🙁
Flash Player 9 no byteArray, so no need think of playing dynamic image processing :((