New layout ideas

I am looking at building a new 2 rail layout. The space is 2 areas. the first is a 15 x 34.6 feet, the second is 9 x 17 feet.   I am looking at using 54 inch and 49.5 inch for most of the turns.  This means that the curves will take 9 feet to complete a half circle.  I need some creative ideas for the layout.   I am thinking if putting the roundhouse and some yard tracks in the 9 x 17 space.  I am also thinking of having a second level.   My railroad will run C44 -dash9s E6, F3, F7, a challanger and GS4.   I also have a Bigboy but I am prety sure the 54 curves will not work!   THe white spaces are the benchwork being built!  Ideas?