Fairly simple game... Someone posts a pic of an actor and says the actor's name. The next person posts an actor whose first name begins with the same letter as the last name of the actor before. So, if someone said Johnny Depp, the next person would post an actor whose first name begins with D... like David Boreanaz. Then the next person would post an actor beginning with B. And so on...
Try not to repeat names too often but if it happens no biggie.
You can also use character names if you want - just make sure the picture u post with it is in character.
Have fun :)