A window sign may be painted on, adhered to, or suspended behind a glass door or window surface, subject to the following:
A. In non-residential areas, window signs shall cover no more than 40% of the window upon which the sign is displayed.
B. Window signs shall only be displayed on first floor windows.
C. Window signs shall only be internally illuminated.
D. Portions of window signs consisting of electronic message displays shall be limited to five square feet and shall be subject to the requirements of section 17-10-19 (electronic message displays).