Shower - outdoor shower. Looks like another pallet and PVC project!
Pergola hammock stand!
30 DIY Ways To Make Your Backyard Awesome This Summer,Build a giant hammock swing
awesome tableside firepit - a couple of these on a deck would be amazing! - total cost to make around 20-25 dollars
Wood planter boxes and bamboo
No trees from which to hang a hammock? No problem -- just build these structures and train vines to grow up and over them to provide shade.
Back yard work shed with loft bed for guests, and a studio for me!
Maybe tie pergola in with another feature/contemporary arch somewhere else in the garden, eg. entry to the veg garden?
@Mel Warren you could totally do this in your back yard!