A small update has hit Google Classroom this week. They have added many more themes and patterns as options for your courses. Also, you can not upload your own personal images to use as a theme!
You can read more about it on the official Google Apps for Education Blog. But here's the main idea...
Also, Google just recently changed the "Incoming" area in their new Google Drive interface back to "Shared with me". I guess it was confusing enough people that they needed to backtrack!
Sean Mullins | District Instructional Technology Coach