I'm not an artist but am happy to mock some stuff up.
This breaks the premise of the "it only takes 5 minutes" but if every card had an "outbound" object (like the pail of water) and an "inbound" slot (like the fire), that could work.
The other suggestion I have is more about the connection points, like, just put a prompt (your visual suggestion is better but harder than plain text) so there's a reason to connect cards to each other. Like, "More serious" or "Similar style" etc.
Just spitballing some more "game" elements. If this is done digitally it'd be quite different than IRL stickers. Also something that would play well on social media would be extra gud?