Unwilling to let the sticky wall go to waste, I pulled out my foam sheets from my stash and cut out some shapes to stick to the wall. I also pulled the contact paper up from the wall and drew on a few details with a marker on the back side of the paper. Here's what we ended up with:
Erik loved this! I purposely made each train car a different shape and color than all the rest. We got to work on expanding his vocabulary by talking about the different kinds of cars, as well as the different colors. It was a couple of weeks before he finally lost interest and the contact paper lost its stick and had to be thrown away. Next time maybe we'll do a road with cars and trucks to drive on it. Or maybe a zoo with different animal silhouettes. Or boats on the ocean. Or anything else we can dream up and that he seems to be interested in.