I don't know about milk as a refreshing beverage in the summer. Sounds gross. My Grandma's might have a different take on that, as well as memories as Diptheria being a threat to the Milk Man. I dig these posters though.
Vintagraph has a great collection of vintage American posters from WPA, WW I & II as well as old fruit box labels and Currier & Ives. All for sale as high quality prints.