I put in 2 shelves along the entire walls, along with the mezzanine.
Mezzanine is where I store all the big things I need less often (ie: tires).
High shelves for things I can see but don't need all the time, lower shelves for things more often used.
I installed a workbench with a shelf above it with under-cabinet lighting.
On top of my workbench is my old receiver with aux input and an antenna for radio, with 2 old (but amazing and loud) 12" cerwin vega speakers wired up to the very top shelves out of reach.
Also, a lot of hooks along the bottoms of the shelves to hang things, and below the workbench an area for the blue box, green bin, and garbage.
To do: paint (last week I patched up all the holes).