Johann Wilhelm, Elector Palatine
Later Schoonjans moved to Düsseldorf to work at the court of Johann Wilhelm, Elector Palatine who was a known art lover and had invited a great number of Dutch and Flemish painters to his court. He painted the portrait of the monarch and his wife. During this period he made many drawings, many of which are still in the Museum Kunstpalast in Düsseldorf. After the death of Elector Johann Wilhelm in 1716, Schoonjans returned to Vienna. He also worked in Slovenia in the "Križanke Church" together with Johann Michael Rottmayr. In 1726 he is recorded in Brno (Czech Republic) where he painted a "St. John of Nepomuk". He spent his final years in retirement in Perchtoldsdorf.