I tried to photoshop it but I failed horribly.
Good, the background is fine as it is. It comes with the location.. if you're looking for a location without the business of a strip mall parking lot, you have to go somewhere else. Maybe industrial, or abandoned, or out of the way. Don't alter the background that much, the signs and whatnot come with the territory. It's fine.
It's generally pretty hard to get super good shots of a line of cars, since people tend to suck at parking. You have to shoot them individually to get any good kinds of angles or framing and more controlled backgrounds. Looking good though..