from what i have found, it is LEGAL to have 35% all the way around and to have a 6 inch banner at the top of your windshield. previously it was illegal to have tint on your front door windows. heres the law itself and the link is below
625 ILCS 5/12-503 from Ch. 95 1/2, par. 12-503
"(a) No person shall drive a motor vehicle with any sign, poster, window application, reflective material, nonreflective material or tinted film upon the front windshield, except that a... ...nonreflective tinted film may be used along the uppermost portion of the windshield if such material does not extend more than 6 inches down from the top of the windshield."
"(2) on vehicles where none of the windows to the rear of the driver's seat are treated in a manner that allows less than 35% light transmittance, a nonreflective tinted film that allows at least 35% light transmittance, with a 5% variance observed by any law enforcement official metering the light transmittance, may be used on the side windows immediately adjacent to each side of the driver."
Illinois General Assembly - Full Text of Public Act 096-0815