Most factory Jeep wheels have 5.5" of backspacing with a few having 5.25". The less backspacing a wheel has, the more it protrudes from the wheel well. So a 15x8 wheel with 4.5" of backspacing will protrude out of the wheel well 1" further than a wheel with 5.5" of backspacing will.
Most aftermarket 15" wheels with the Jeep's 5x4.5" bolt pattern have between 3.25" and 4.5" of backspacing so any of those will create a wider stance. The least amount of backspacing I'd ever go with is 3.75" which is very common with most 15" aluminum wheels.