(おもて) Surface. The emphasis is, “This is the FRONT surface, as opposed to the hidden side.” (opposite:裏 うら). Usually used about 2-dimensional things (paper, walls) but can also be used with the ol’ 建前:本音.
(めん) ENTIRE surface of a 3-dimensional object.
(つら) A yakuza slang for face: I can’t believe you’d dare show your face around here!
(ひょうめん) A literal surface – unlike 面 (men), 表面 is more technical – usually used by architects or craftspeople. Or, for instance, to describe a “skin” you’d put on a polygon 3d character.