Check out THE CURT TEICH ARCHIVES. (Select the Lake County Discovery Museum and do a search on postcard images). You used to be able to view the archives at the museum but access was limited a few years ago. Seeing them online is the next best thing.
Sadly, I was unable to find my fave postcard - one from the Frigid Fluid Co. of Chicago - manufacturers of embalming fluid - with a little cartoon syringe man full of fluid, tipping his hat and cheerfully declaring: "I'm coming for you!". I did find this, though:
