I am learning Composer 2016. I think I did something while watching the VAR's tutorial and playing with my model that changed the background image to show the CATIA logo. Notice that the Background image path is not pointing to anything:
If set the path to point to an image file it puts an image into the background but still leaves the CATIA logo also in the background.
To get rid of that chosen image file I use the delete key to remove the text path. But I can't get rid of the CATIA logo background. it doesn't seem to be working on the other laptop that I also installed with Composer.