This just in from my dear old dad:
I was at an international poster show today, just browsing around. It was made up of a number of galleries from all over the country, including more than a few from Europe. One of the galleries, from Switzerland, had placards detailing the name of the poster, the country of origin, the date the poster was printed, etc. Oh yes, and the artist's name. One of the names jumped out: "TIECHE." Now there aren't many people in this world with that name and certainly not a lot of artists from Bern, Switzerland with it, let alone a successful artist with that name. I was told Adolphe Tieche was a very famous poster artist around the turn of the century. His work is well-regarded and highly respected among aficionados. The poster was selling for $4500.
Here are two examples of his work (the Zurich poster was the one I saw):
...and as Kristin so rightly assumed, the actual pronunciation of our last name is Tee-esh.