Martin Andrews puts on frequent displays from the ephemera collection at Reading University. A recent one was of old letterheads - the sort with a picture of the factory, and illustrations of key products. Some of them were so full of pictures that there was very little room for words.
Here's one from my own modest collection (of two). What strikes me about letters like this is how similar they are to modern marketing emails, with a central message surrounded by pictures. And the references to telegrams in the letter reminds us that fast business communications have been around for quite a while.
I bought this example from the wonderful Ken's in Newport Pagnell, when our company was based there. Not just a motorway service stop, NP was also home to Information Design Unit, and William Cowley's parchment works, one of the last left in England.