[1] At about this time, Cassiers went to live in the fishing town of Knokke, where there was a large artist colony which included Alfred Verwee, Louis Artan, Flori van Acker, Franz Courtens, and later Alfred Bastien and Firmin Baes.
He had successful exhibitions in Brittany, England, Switzerland, Germany, Italy, and other countries.
[1] He established his focus on commercial illustration, and his work was featured in well-known newspapers, magazines, hotels, restaurants, and resorts.
[2] He designed many posters, notably for the Red Star Line, a shipping company of Antwerp, his main client.
[3] Some of his most notable work was for Le Patriot Illustré, and his posters include several for the seaside town of De Haan.