To truly make strong backgrounds and environments, you must first learn a few basics.
Build Your Glazes
When developing an environment you need to understand values and glazing.
Glazing is when you add one layer of paint, let it dry, and then add another layer of transparent paint. Think layering colored tissue paper upon each other.
Applying Values through Glazing
Let's begin with an exercise. Draw/tape a square, and to the right make 6 small rectangles, numbered 1-6.
Lay a wash down by pre-wetting your paper and adding an even layer of color.
For this I'm adding clouds using a tissue to blot to the white of the paper.
Next I'm going to fill in the rectangles 2-6 with the same color I just did a wash with. This is my first glaze.
Once dry I will take the same color, same amount of water to paint ratio, and add a second glaze. This one will be the one to determine the horizon line.
I add salt to give some texture...
And I add some water around the horizon line to add more texture/atmosphere.
Once dry, I go and fill in rectangles 4-6 with another layer of paint. While also adding another layer of paint in my landscape on the left. More water drops and salt. I'm also aware of what happened in the previous glaze and work around what had dried. Picking and choosing what I'd like to keep untouched.
Let dry. The last two glazes I added a bit more blue to intensify the color and to add some kind of visual interest in color. You don't have to do this. Yet, I would make the water to paint ratio closer to milk/yogurt to make sure these layers are dark enough.
Because this is starting to look like a field of some sort to me, I chose to add large flowers using rubbing alcohol in the middle ground.
For the 5th layer/glaze, I take my time and create stems. Because the previous glaze is now dry, I can "draw" with my paint and fill around. This is called negative painting. Where you paint around what value you want to keep.
Finally it's time for the last glaze. Everything must be dry to add this layer. Hair dryers can speed up the process by putting it on high heat, and about 6-8 inches from the paper. Careful, if it's too close it'll fade your paint. ;)
In the foreground I make simple brush strokes with the round towards each other downward to create the 'feel' of leafy shrubs.
Most environments and atmospheres I create are using this approach, whether covering a place or just a 'feeling'. The adding of textures, techniques, and glazes truly make it simple and fun!