While there are several routes you can take when designing scenery, or characters for that matter, the following are a couple of tips that may help you when planning out your scenes:
Keep the outlines of your backgrounds lighter or thinner than those of your characters. At the very least, don't make your background outlines thicker than that of your foreground objects. Of course, this doesn't apply if you decide not to use strokes at all for your designs. However, this technique will allow your foreground objects, such as characters, to stand out more while animating your cartoons. If you're using black outlines for your characters, you could probably try changing the color of your outlines for the background to see if it provides more of a pop. The following screenshot demonstrates how lines and colors can clash with background objects if not careful:
The same concept applies for fill colors. If you have bright, vibrant colors making up the background, they could wash...