I mostly store decorative items that I had to move to make room for new things. Or if I bought it to see how it looked then didn't like it, I'll store it away in case I want to use it later. I have a lot of nature items in my inventory, and some benches and fences, parking lots, of course some extra CoC stuff I couldn't find room for, 57 Jack-o-Lanterns, some Fleet-a-Pita vans, a Bloodmobile, and some other random decorative items. I don't keep anything in there that could earn me money, and I like to have all my NPCs out too.