Haven't finished rebuilding my current layout and I'm already looking at the next one! This spring/summer I plan to get the garage ready for my layout. I'll be able to build up to 18' long, 6' feet wide. I'll have access along the two long sides and one end. My design "must haves" are:
1) Ability to run 3 trains with 2 of them being connected.
2) Reversing loops - I get bored watching trains go around in circles.
3) At least one elevated loop.
4) A mountain/tunnels.
5) Room for plenty of operating accessories. Right now I have the K-line milk depot, Lionel sawmill, AEC nuclear reactor and AF oil drum loader. I also want to leave room for the gantry crane.
6) Space for a ramp leading to a below table sorting/storage yard. Probably want this to be along the 18' side to keep the grade manageable.
7) Would like to avoid the nested ovals/bulls eye look as much as possible.
8) No long reaches to operating accessories - the space under the table will be used for storage so an access hatch is out of the question.
Other considerations: I have no minimum curve requirements - all my locomotives will handle O36 and much as I'd like to own a veranda turbine or centipede I can't see every dropping that kind of coin on a locomotive. I don't need room for a town and a bunch of buildings. Not interested in prototypical operation - for me it's a toy train set, not a model railroad. I'll probably go with Atlas track since it's readily available and looks good. The under table yard/storage are will use my existing FasTrack.
I've been playing with some ideas in SCARM but would love to see fresh ideas from other people.