Your viewers type !coinflip heads or !coinflip tails in your Twitch chat — the coin flips on stream and shows the side that wins.
Picture: paste an https link to a PNG/JPG/GIF (e.g. Imgur or Discord) so OBS can load it.
OBS: Sources → + → Browser → paste the link, 800 × 800. Reads your Twitch chat only (no login, never writes in your chat).
Live preview — a sample viewer flips every few seconds