That will definitely work to change the course image that appears on the tiles of folks' Canvas dashboard!
But it sounds like @LKV, the course you are looking at did some unique customization of their course homepage and built in images/tiles that will redirect you to a specific module? They would have done this through editing the HTML of the course homepage, or using an external design tool to build their Canvas pages. Unfortunately these aren't built right into Canvas, so you will want to reach out to whomever created the page you are referring to and find out how exactly they built that page and how to change those images.