Post a pic from any anime you want. If nobody can guess it, then drop a hint every day or so. Good hints are usually, what genre it is, what the title starts with, who produced it, etc....
If you guess and are absolutely certain that your answer is correct, go ahead and post the next picture in your reply.
If you are not sure if you're right, then just wait for a reply before you post the next image.
If you find that someone answered yours incorrectly and posted a new pic, then say so and repost your pic, and an admin will delete the posts above it later. The person in the wrong may then use their pic at another time.
If you guessed correctly & the answer was given, post your new pic within a week or you will forfeit your turn.