A three industry layout that I would consider consists of the following 3 industries:
Food Company:
Inbound - Covered hoppers, corn syrup tank cars, cooking oil tank cars, reefers, box cars, and RBLs.
Outbound - RBLs
Manufacturing Company:
Inbound- Flat cars, box cars, gondolas, tank cars, plastic pellet hoppers, and coil cars.
Outbound - Box cars, flat cars, and gondolas.
Building Supply Co.
Inbound - Hoppers, cement covered hoppers, flat cars, box cars, and gondolas.
Outbound - None.
I also have a track plan that I mull over. it fits in a 10 foot by 12 inch area. I used Atlas Snap Switch turnouts, but if you use Peco turnouts (especially a 3 way), you gain extra switch lead length. Like Prof. Klyzir mentioned, angling it a few degrees counter-clockwise would also make it visually more appealing.
The lowest track could be used exclusively for building supply and car storage. I would store the locomotive on the lead to the manufacturing plant.