building toys may help, those are more free form (magna tiles are extremely popular here, even for older kids, and I have seen them in the 3s room in the daycare our kids went to all the up to K/1st grade - we have a huge stack that we got when our oldest was 3 and even though he is 6, he still loves to play with them). IO blocks may be interesting too if he is not prone to get mouthy with stuff. DH has gotten butcher paper to scribble at dinner table and huge brown roll for DD to go crazy with art.
