I was looking to sell a vehicle that I purchased over the CP exchange. I was wondering if a Shopping Center can act as a Marketplace location, or is there another building type that I need to look for.
At the moment it is not possible to sell entities to the NPC market.
If you want to sell it to another player, either make a post in the Commerce forum board in the RPG Center, or use one of the faction run markets such as CPM: http://market.centrepointstation.com/
If you want to sell something to the NPC market, you will need to be in a Commerce Centre or Trading Station. As all of them are player/faction owned, you will need to either ask around, or find one of them yourself.
(Hint: Commerce Centres and Trading Stations can be built by Trading factions.)