Hello John, and welcome to the Gnatterbox.
My first thought on reading your post was "do you have any depth to play with"? In a long, narrow space like that, I'd be thinking of a mine entrance at one end (open at the back end so you can load / unload cars with timber / miners / supplies in and ore out from the mine without making it too obvious), then over a bridge (hence the thought about depth), to a loading / processing / transfer plant at the far end.
You could do the same with timber - forest at one end, sawmill at the other, with a bit of a journey in between to give the loco something to do.
Also, with 9' x 30", you could add a shed for the engines, as well as fuel and maintenance provision.
You could also quite easily by using tight radius curves and short locomotives / stock have a circuit of track (30" is very generous in Gn15
) if you want to watch the trains go round and round for a while instead of actually operating the layout.
Sector plates or traversers at either end (please see my "Huge Tools" thread for a plan incorporating two sector plates) are also an option if you want to go end to end.
I hope these rather garbled thoughts help - whatever you decide to do, please keep us informed, and we looooove photos