M.B.
Boxes are wonderful things to stimulate imagination! If you can get a large box, one big enough for him to sit in, have him decorate it... it can be a space ship to the moon, or a wagon in a wagon train.....
My grandson, the other day, found a box.... it was a bit small for sitting in, so he dumped his blocks, blankets, and other toys, and took it around the house giving us "presents"!
He is 3 1/2, and his imagination has just been blossoming lately!