One thing I need to overcome in my art is the horrible American mindset that backgrounds aren't important, or necessary. Most "professional" American comics will use a background to establish setting, then, if the artist can get away with not drawing it, they don't draw it. Sometimes for 4-5 pages.
I just read a preview of a "professional comic" where the first page, a splash page, established the setting, then the next 4 pages were fighting in blank, or wonderfully colored panels. A hint of surrundings would make it into the panel if one of the baddies had to get punched into a crate, or pick up an object. That's like watching THERE WILL BE BLOOD and the entire movie was played out in front of a blue screen, and the only time you saw a background was in a pulled back establishing shot or if a character picked up something/touched an object.
I'm not saying every panel needs to be filled with richly detailled backgrounds, but it should serve the story if there isn't going to be a visible setting. Lack of background can create mood, atmosphere, emotion. Like color, it can be used as a weapon in the arsenal of storytelling.