Always make of empty space and this includes the space on the back of your bathroom. You can hang towel holders down the length, giving you room to keep several towels and washcloths. Use lower racks for small children so that they can get to them easily.
Instead of putting your hand towels on towel hook, consider using large antique door handles. This might work better for a smaller spot on the wall where a bulky towel hook won’t fit. It is also more secure and the towel is less likely to slip off.