Clark
John Armstrong once wrote an article in Model Railroader (in the '50s) which pointed out that most model railroaders generally operated their layout in one of 3 ways, depending on their personality and preferences. Particularly in a relatively confined space such as yours, you'd probably be better off aiming for one type of layout instead of a hodge-podge which doesn't satisfy any operational style well.
The first type is the spectator. He likes to see his train run through a beautiful (to his eye) scene of some kind. The spectator is not particularly interested in doing a lot of switching or dispatching multiple trains around each other, although on occasion that's fine, too. His particular interest is watching and photographing his models in a realistic setting.
Second type John Armstrong talked about was the engineer. This guy sees himself as a one man show running a train from start to finish. He makes up his train at the yard, simulates the selection and servicing of an engine, takes the train out, switches industries along the way, then breaks up the train, and puts the engine to bed. The engineer enjoys switching, doesn't mind a lack of a continuous run capability as much, and generally is a little more accepting of crowding to get operational features than the spectator.
The third type discussed was the dispatcher. The dispatcher prefers to be the director and coordinator of multiple trains, each having a part of the action. Often, he will have other operators join him to be the individual engineers of their trains while he assumes the dispatcher role. Very much the operations-oriented model railroaders of today.
Obviously, very few of us are hard-core matches to any one personality type. But each of us usually tends to favor one style over the others, even if slightly. Knowing which one suits you best is important for your choice of track plan and long-term enjoyment.
In the space you have, a dispatcher-type layout is the most difficult to achieve. To achieve mult-train operation in your space will require careful planning and a fair amount of crowding. But I've seen it done in 4x6, so take heart. At least 2 passing sidings, multiple routing, and some industries to switch are the order of the day.
The spectator layout is usually easier to plan. Look for uncrowded plans - or blow one up from a smaller space - that feature a particular scene you want most to see. Whether it's one train crossing over another on a bridge, a train crossing a spindly trestle, a busy harbor scene, a locomotive emerging from a tunnel - whatever scene strikes your fancy should be the highlight of your layout. The rest of the layout should be staging to repeat the desired scene. Dummy tracks, continous runs, separate ovals on different levels, double track, staging tracks are all acceptable means to achieve the spectator's goal of recreating that vision or memory. If you can fit 2 of your desired scenes in, so much the better, but the spectator will be happier with one memorable scene done well than 2 crowded scenes that aren't quite what he had in mind.
The engineer layout has to have a little "yard" and some industries to switch, which pretty much limits what can be done in a small space. Because continuous run is not essential, you can, as an alternative to the oval, view your space as 2 separate 30in by 5+ ft shelves joined by a semi-circle for planning purposes.
Your reaction to various published track plans will help identify your leanings. I tend to the spectator/engineer combination, with very little dispatcher interest at all. Others are very different than me, and that's great.
Hope this helps.