So! Because we're all doing comics here, let's get this out of the way: If you're doing backgrounds for comics, don't be afraid to try and use shortcuts or minimize the details of your background (half the time, readers aren't really paying attention to that. It's a great way to establish a scene, however!)
That being said, one of the things I've done to try and do more backgrounds is to just... do them. They're not always perfect but they get the job done.
Couple of things I would recommend:
- Use the Sims as a background/room generator. Draw over it/Reference it and try adding characters into the scene or personal belongings. This helps you figure out which angles work best and how to 'dress' your scene.
Paint along with Bob Ross. You'd be surprised at some of the techniques you begin picking up from painting along with him. If you're doing a lot of outdoor scenery, this is a great way to get your hand used to the strokes and techniques a lot of painters use. It translates pretty well into digital, and once you get the hang of it, you can start on your own!
Can't go outside? Visit free stock image sites like Unsplash for high-res photos of cities/landscapes/etc. These make for fantastic references for practice, and if you're coloring along, helps you figure out how lighting/reflections work too (and also building up a neat color scheme, as a lot of the photos lean on the artistic side).
Start small: Draw a couple of pieces of furniture together, say an armchair and a side table. Then expand towards the rest of the room.
Perspective can be tricky: And what I've learned is that sometimes what is right tends to look wrong. Don't be afraid to skew the rules just a little so the drawing looks more aligned.
I hope these tips will help you! Good luck ^w^/