Building an outdoor bike storage solution

I have a metal shed in my front garden, which can hold three bikes easily. However, we have five bikes between us. I can't easily fit another similarly-sized one in the back garden as they take up a lot of floor space. A couple of the bikes aren't used on a regular basis so could be stored in the back garden upright. Does anyone recommend tall and thin sheds, or another method of storage?

Are the bikes in the existing shed positioned most efficiently? For example, hanging bikes on a rail of some kind?

You could also make a tall shed in the back garden which has 2 levels of bikes, so uses less floor space. A lean to is a good idea, gives you something strong to hang the bikes on.