The regulation references Illinois Code 430 ILCS 66/1, which I emboldened below, while the example sign shows Illinois Code 430 ILCS 66/65. It appears that either citation could be acceptable. I cannot find any verbiage in regards to the orientation of the sign.
”Owners of any statutorily prohibited area or private property, excluding residences, where the owner prohibits the carrying of firearms must clearly and conspicuously post the Illinois State Police approved sign, in accordance with Firearm Concealed Carry Act, at the entrance of the building, premises or real property. Please refer to Section 65 (Prohibited Areas) of the Firearm Concealed Carry Act for more information on statutory requirements for signage as well as where concealed weapons are prohibited.
Pursuant to Section 65(d) of the Firearm Concealed Carry Act, signs must be of a uniform design and the Illinois State Police is responsible for adopting rules for standardized signs. The Illinois State Police has proposed rules which require a white background; no text (except the reference to the Illinois Code 430 ILCS 66/1) or marking within the one-inch area surrounding the graphic design; a depiction of a handgun in black ink with a circle around and diagonal slash across the firearm in red ink; and that the circle be 4 inches in diameter. The sign in its entirety will measure 4 inches x 6 inches”.