Creative uses for the Backyard Space at my property

[Inno Ekeh]

I have a 4plex in Sacramento CA that has been stabilized and cashflows well. The property also has a size-able backyard that shares a border with an alley. Ive since had a fence built to protect the property, but now I just have open/unused space that I am paying for. The current economics (leverage, building costs, etc) disallow venturing to build more units on the land. 

So I am wondering what creative solutions I can implement to cash flow this open space. Any suggestions are welcome.