"No tops, no bottoms" is a reference to EP4. In that episode, Lars recounted the events of a hook-up and the ensuing chaos. This included photos of a certain nature. Alexis put on an investigating voice, asking if he was talking about "tops" or "bottoms", or in other words, if these were photos of the top or bottom half of the person.
Since then, "no tops, no bottoms" has become slang on the show for "this photograph is appropriate" or, more generally, "everything is on the up and up".