Decorate a bathroom with shapes and materials that evoke the rustic simplicity of real lighthouses: beadboard painted white, gray or pale blue on walls; brass fittings and fixtures; a half clamshell with a smooth beach stone in it as a soap holder on the sink. A touch of nautical decor, such as a row of semaphore pennants over the shower curtain or a coiled rope bath mat, is more effective than over-the-top, everything-lighthouse kitsch.
Hang an antique life preserver on one whitewashed wall. Search for one with obvious wear and remnants of a stenciled ship's name and original rope handles, such as a preserver that might have been fished from the sea by a lighthouse keeper. Replace a window in the shower with a porthole, framed in antique brass, and substitute an old-fashioned brass showerhead for a standard chrome one.
A narrow wooden tower with a stack of shelves, painted to look like a lighthouse, holds rolls of toilet tissue. A piece of driftwood painted with the name of a lighthouse and fitted with brass sailboat cleats is a towel rack. Frame nautical charts to hang as art, or paper one wall with them, and protect it with clear polyurethane.