Most dryers can't be pushed up against the wall due to the dryer vent so why not build a shelf to cover the gap. Not only does it add more storage but it also keeps items from falling behind the washer and dryer
Here is the vertical cedar fence my hubby built (with my design, lumber shopping and staining help - Im useless with a hammer though) to cover up the two hideous air conditioning units gracing our frontage. Hes awesome! Im happy. We left lots of air for the AC units to breathe so hopefully its fine.