Signs regulations, including provisions to control the type, design, size and location thereof, are established in order to achieve, among others, the following purposes:
(a) To promote attractive and high value residential districts by permitting only nameplates on single-family lots and by permitting only nameplates, bulletin boards and real estate signs for other uses in residential districts;
(b) To provide for reasonable, and yet appropriate, conditions for advertising goods sold or services rendered in commercial districts by relating the size, type and design of signs to the type and size of establishment; and,
(c) To provide for appropriate signs in office and industrial districts.