Striped wallpaper can be problematic if the stripes run horizontally. This only encourages a low level view and draws the eye across rather than up.
You should avoid large furniture in low ceilinged rooms. Armoires and high-backed chairs only emphasis what you are trying to hide --- the same goes for large furniture upholstered in patterned fabric which creates a busy look in a closed-in area.
Crown molding is often a beautiful and sophisticated addition, however with low ceilings it only adds to the design problem. You should only use very thin crown molding.
Low ceilings should not have down-facing lighting which will make this space feel closed in. Avoid recessed and pendant lights.