Buying an outdoor storage building with a loft greatly increases storage capability, allowing you to store rarely used supplies overhead. For the exterior, build your own lean-to and attach it to the outdoor storage building to form a sheltered area for firewood.
Clean It Out - With any organization project, you'll want to remove everything to start fresh. This goes for your shed as well. Toss any old items or trash to declutter your space. If there anything you haven't used or your family has outgrown, now might be the time to donate or sell that item. Though removing everything from your shed might seem counterproductive, it's better to see what you have to store before you create new systems for it.