Bit late responding to this but the image is a solid star in the middle of the picture. You need to relax your eyes and look through the picture, kind of as if you're focusing on something behind the image, then it will eventually pop out. If you've got a reflective screen then focus on your reflection and gradually defocus back to the screen surface and that may make it work.

Some people can't see them though so I won't post any more but if you search 'Magic Eye' on google Images there's loads of good ones and some are probably easier to see than the butterfly one.