Alright , This is pretty simple .
The first person asks for something in a picture.

Ex.There must be 5 trees in the next picture.

So all you have to do is find a picture with 5 trees. Then once you find one you get to say something.Then the next person has to go & find it. Get it?

Example:
User1:The next picture must have a clown in a car.
User2.
*picture of a clown in a car*
The next picture must be of elephants playing soccer[or football;depends.]

Alright? So I'll start .
The next picture must be of A fancy dressed Chihuahua