Well, if you have a grain boxcar and an F7A, I assume the setting of the layout would be perhaps 1970's or before. I imagine that like any model railroader you'll gather more rolling stock before long.
But with what you have, you'd have the sort of short local to service a small farming town: one with, say, a grain silo (to fill the boxcar with grain), a fuel dealer (which could be represented with a shack, a couple of hoses and a small storage tank or two, or even just a tanker truck sitting by the team track to be filled directly from the tank car), and perhaps a farm-supplies/tractor dealership. These businesses could be reached via a couple of spurs on one side of a small layout, with perhaps a runaround track to allow facing-point switching.
Most such towns would typically have what is called a "team track", usually just a small elevated platform with a ramp to allow railroad cars to be loaded. Just about anything could go in or out on the team track: those tractors, for example. Obviously it would be tough to load bulk grain there but that's what the silo is for.
The other "side" of the layout (whether it's the far side of a loop plan or the other end of a shelf layout) could be a larger town with a mill and other industries, or you could just represent incoming traffic via an "interchange" (where one railroad meets another, and cars are shuffled back and forth for long-distance customers.) New cars could be brought in via the interchange, or sent "off" the layout in the other direction.
A farming town themed layout implies someplace where farming is done: the Midwest, California's central valley, etcetera. Pick the sort of place you prefer and check out some photos to get ideas for scenery. Rolling hills or flat plains would be a good fit and not too hard to model.