Practice without direction isn't really going to get you far. Try to figure out what it is that isn't working before practicing that thing, and try out some focused practice, not just finished pieces. So, for the backgrounds, for example, what is it that's bothering you about them? Layout? Keeping things balanced so that it doesn't overwhelm the foreground? Lack of skills on drawing the things that tend to go in backgrounds? Don't just focus on what you're weaker on, try to figure out why you're weaker. You'll improve much more quickly that way.