I'm bad at decoding cypers. However I have been able to make them with photoshop. Any picture can be be used to put a layer of text or another photo then lighten to impercptual visibility and flatten. The way to recover the information is to to put the picture through several rounds of maximum contrast. Variations using color also works by using saturation and contrast or inverse color enhancment. Subliminal messages can be done by not going all the way to imperceptability or in video the same old single frame technique with some new gimmocks.

Using photos of uniformity like clouds and sky are the easiest.
Today's photo