For the passenger side rear I'm using wall mounted black garage cabinets that are supposed to take the hot / cold weather change pretty good.
Most all stock ATV fit between a truck wheel well (4ft), I wanted a little extra room in case we have a wider than stock ATV parked in the shop area.
So the 12" deep wall cabinets worked great.
I made a tow kick, wrapped it in the coin rubber flooring and bolted it down, I than stacked the cabinets till I found a configuration that worked for me. Also I hung some coin flooring on the back wall above the cabinets. I'll use this space to hang spare props for the boat.
I would also like to use Aluminum "L" angle in all the corners, I think that will be a nice clean look and much more durable than wood.