Depending on the location of the warehouse, you could make it a commercial building and do some trading activities on it. Another possibility is converting the warehouse space into an art gallery. This is sure to bring in some money since the world currently is flooded with artists who are willing to take such an opportunity. You could also lease your warehouse to a company, this way you don't need to worry about finding clients for each square foot of space.
We have a local warehouse called That Bouncy Place. They have multiple giant inflatable bounce toys (like moon bounce and slides). We take our daughter there and she loves it. We have to sign a waiver before she can play (so that they are not liable for any injuries). They have lots of birthday parties for youngsters and I also heard of an office having their party there with kegs of beer. If I had the space, I'd so start this type of business. They literally roll in the dough and that's only charging about $7 per kid for one hour of open bounce or around $200 for a birthday party (1 hour of bounce and 1/2 hour in the party room). Check out www.thatbouncyplace.com to see exactly what I'm talking about.