having man made collectibles would be interesting! especially if part of the next game were discovering the previous inhabitants of the island

i liked the gong in 2, although i don't really want the next set of puzzles to be about collecting individual items

maybe the last puzzle in the next game could be collecting beads and shells that pop up as other puzzles are completed, or as different building jobs are completed - one piece could be found under one of the strange plants, one could be found in the partially completed first hut, one could be found the first time someone fishes, etc a couple could be random rare spawns maybe

or it could be a statue, like the idol from the first VV with jewels missing, and what they are finding are the jewels, and they replace them, when all are replaced then a passage opens or some other wonderful event!