That kit is sure looking less like a kit. Nice job.
If you want to add some authentic detail, add some cyclone seperators on top of the smaller shed/ sack building/warehouse. Four or five would work. WS had a small kit for a steam powered hammermill with a seperator. If that kit is still available, I'd take the hammermill part, rust it up and lean it outside (after the buildingings are set) in the weeds.
I've never done it before, but a convincing seperator(s) cones could be massed produced using dowels and a pencil sharpener.
If your mill makes feed pellets add a small boiler room. You could use the boiler from the WS kit set in a small lean-to type shed.
NOTE: grain is abrasive and will wear down the sheetmetal pipes used at driers, bins, elevators. So, toss a bunch of rusted pipes under the sack room's raised floor. Wood planks have a tendency to get piled up under there too.
Bundle up some dowels to represent bundles of fence posts for sale. If this a contemporary layout, make up some modular fence panels and stack them up.
A few toilet paper roll wooden silos would be a perfect addition.
My $.02.