Also on these boards
Now THIS is one I haven't seen before. What a great idea! Might have to do some little footprint trains or firetrucks too!
Tractor footprint art. Get their little footprint onto some white scrapbook paper. Then print off a tractor image online, you might need to blow it up to fit the size of the footprint. Cut out the tractor pieces and trace around footprint with a pencil and paint. Could be done with anything I bet. The link on this is the tractor I used to trace