This got suggested many times before by myself included.
Some ideas just from the top of my head:
Like I suggested a long time ago a game like Flappy Curve
A free field where you can draw with your line
Curve city! A big field ffa for everyone who is ready in the queue kinda like Skirmish in Overwatch. With basically instant respawning etc.
I mean whatever it is it should be definitely fast paced so no matter how long you are in the queue 20 seconds or 2 minutes that you can have an enjoyable experience.
The better this minigame is the less people mind being longer in the matchmaking to find the best opponents in a similar rank range. So I think a proper minigame would add an huge value to overall CFP.
EDIT: Right after I just thought of the second one I realize what a great pictionary game it could be. Small turns and fast speed and simple words to draw. One draws and the rest in the queue guess it.