I have played w/ stego some and w/ the present resolutions of images I dont find the images have enough complexity to really hide a message of a useable length, unless you break it up into several images. I use a function to measure the complexity of a image based on adjacent bit changes. The more complex an image the more bit changes. I measure it thus: # of adjacent bit changes in image/ # of bits in image = complexity if the complexity is too low or too high (this is counter intuitive) then you can't hide a message. Consider an image w/ only a few bit flippings, any message that is inserted will cause the visual image to be distorted in a noticable way (unless it is truely expressionistic). Now consider a image w/ every other bit flipped (maximum complexity) which is in effect a checkerboard. Any bits that get flipped change the pattern to a less complex one (ie the checkerboard is broken up). Also you have to consider the effects on edges and the standard deviation inherant in using anti-aliasing. This will cause bits on the edge to be switched incorrectly for the algorith in use. Since it is a trivial problem to measure the sd for various graphics packages this makes a nifty test bed for finding imbedding images. Blank or mono-chromatic areas also show the same type of errors. I am still working on it and hope to find an error in there somewhere but so far no go.