We have a huge wall full of PBK Cameron system. Love it.
The bottom row is a single row of drawers (great for hiding odds and ends and little stuff)
On top of that we have open cubes. (2x2) Great for books and Montessori style toys- puzzles and things. Easy for the kids to reach and out back. One of the cubbies has a basket with mr potato head stuff.
On top of that we have the cupboards with doors. Play, board games, art supplies, and other hard to organize or needs supervision things are in here.
Finally the top most row is another set of open cubes. Bigger kid books for when they are older, craft/science books and kits, as well as photos and decorations.
It's worked out really well for us! We have 3 verticals, 4 rows. Takes up most of one wall of the playroom and looks great!