"Universal" jigsaw piece - connects to itself on all sides Rejutka

This is mainly a base to build upon, i.e. a blank slate.
There are connectors on all sides, so each side can hold another tile (in theory).

Unfortunately, since you have to twist them to connect, you can't really have a tile on all four sides, you'll need the "placeholder" tile to add the fourth piece. It has no outside connectors, so will always fit - on top are the connectors it should have on the side, so you can add another tile on top of it.
Not pretty, but it works.