I once made a music player similar to this. It converted music files into image files, and saved them to Flickr. One trick that I employed was that the output image files were also visually recognizable, featuring album covers and lyrics.[1][2] The way I used to hide information was pretty barbaric, but it was still a fun experiment.
[1] https://www.flickr.com/photos/barosl/albums/7215763383971356...