This game works like so:
A poster posts a picture. It can be of anything, not necessarily pokemon related pictures.

The next poster posts a picture of something that "beats" the picture.

For example, poster 1 posts a picture of a fire. The next poster posts a picture of something that beats it. Like a fire engine. Or perhaps a Blastoise.

And the game goes on from there, the next poster posting their image and so forth.

Obviously all SPPF rules apply, so keep the pictures appropriate.