Bit of an IRL carpenter, so here's a take on wooden pegs. Best ones are made from branches using a knife. Most anything that uses a nail can use a pin or peg (even tiny things). Also the mod needs to include the very basic new 'stone age' tools (flint saw, stone knife, etc.).

This could expand to a great mod by simply allowing 'wood based' solutions (via primitive tools as well as advanced one). Like glue from hooves, there's a thought.