According to the hymn board, it is Trinity Sunday. The Hymns from that Sunday were 19, 517, 428, 245, and 538. You might have to get into the archives to answer this one.
The note on the back reads, "St. Paul's Church, Klamath Falls, Oregon. The background is a lovely blue. The central figure is Christ the King with His right hand raised in blessing and His left holding the world. Around the Christ are the shields of the 4 Gospels. Lower left = shield with Chalice, - l. rt = open Bible. On side walls are shields of 9 dioceses in the first general Convention. The border background is gold".