There is nothing more creatively stultifying than having a "style". Your style should be constantly growing. When you get used to one style, get mad at yourself and discard it for some new ideas. This isn't easy, but it's more fun than stagnation.
There is no greater evil in cartoons today, than that a show show should have a style. Look at old cartoons and take inspiration. In the 1930s to the 1950s the cartoonists constantly experimented with the looks of their cartoons-especially with the background styles.
A lot of background artists didn't even come from animation. Many of them were illustrators that didn't have pre set notions of what cartoon BGs should look like. Of course they couldn't completely dictate what they would draw and paint. That was the director's job.
The directors of the past would work with them to guide the artists to compose their BGs functionally to help make the characters and stories more effective. But the directors were very open to the BG artists creating their own looks.
A lot of people think that Ren and Stimpy had a style. It didn't. Go back and look at a couple episodes back to back. You will see many different Background styles and character styles too. We constantly experimented and tried to outdo each other and ourselves.
Background styles can and should vary wildly. It's fun to experiment. Just make sure the BGs serve their functions-they compose around the characters, give mood to the stories and tickle the eyeballs.
Don't let the executives tell you that kids crave a consistent look. They don't. Smash the exec in the face and tattoo this post on him, tie him to a chair and make him watch 5 Bugs Bunny cartoons in a row so that he can see that the only consistency there is in a good cartoon series is a consistent desire of the artists to change and get better.
Avoid "wonkiness" and chaotic uncontrolled messy backgrounds, because these will distract from the characters.
Controlled variety is the goal. And fun!