There haven't been any new threads posted here for a month - so let me suggest a couple from Cassandra that will appeal to jigsaw-puzzle fans. You make a bet on your time - before you start - and then get the tasks you bet on if you win (faster than others) or lose (slower than others). And you get to do the tasks for each other person who tried those puzzles!
The Challenge:
https://www.getdare.com/bbs/showthread.php?t=339001
Three evil puzzles:
https://www.getdare.com/bbs/showthread.php?t=341974