I've made a few 4x8 N scale plans that you can use or modify if you like. (Click on any of these to enlarge them)
This one is not quite 4x8....
This one was done in HO, but for N you could redo the yard and make it proper...
This is a 4x8 N scale that I played around with a bit and made some different track arrangements. Some are better then others. Some even have a two track staging yard under the scenery......
You can also take any HO scale plan, change the track centers and build it to N scale.
Now that I've got you thinking, let me show you something that might get you really going!