Throw one back

If they never send one back, you posted a picture. You did not start a conversation.

The return is another picture

A send asks for a return. Not a paragraph. A picture. They see themselves, and the answer is the next meme, aimed at you. A like does not count. "haha" does not count. Another picture does.

You do not need a new idea to reply. Use what they just did. They sent the dinner. You send the empty plate. They sent the story. You send the ending. The reply should be obvious to the two of you and slightly confusing to anyone else.

Do not chase

If nothing comes back, do not send three more. A stack is pressure. One unanswered picture can sit. Two is a bit. Four is you performing at someone who left the room.

When they do throw one back, stay in that chat until one of you brings it to the group. The group gets the joke that already worked, not the draft.