Images have a lot of data - probably more than most audio files, in general, unless you're talking about a pretty small image. that makes this a challenge. The term to search for is "steganography", although most often that is used to hide text in images (where the data ratio is more favorable).
I don't see why not. After all the audio file is going to be a small amount of structure and a larger amount of bits which are unrestricted, so you could put the bits from the image into those unrestricted places. The audio file isn't going to be something you would want on your MP3 player, but then that wasn't one of your stated objectives.
subject: is it possible to encrypt an image into an audio file using java?