No sign may be erected or maintained that:
     (a) Imitates or resembles an official traffic sign, signal or device;
     (b) Is erected, painted or drawn upon trees, rocks or other natural features;
     (c) Is structurally unsafe or in disrepair; or
     (d) Is erected adjacent to a scenic byway that is a primary or Interstate highway after the effective date of this amendatory Act of 1996, except those signs described in Sections 4.01, 4.02, 4.03, 4.06, and 4.08 of this Act.