here's a good "after" pic..
Not trying to bash what you want to do with your jeep, but in all honesty I'd suggest saving your time and getting some rims with proper/better backspacing. A "good" set of spacers (if there is such a thing) will run around $200.. for that same price you can buy a whole set of steel wheels from summit racing with 3.5 bs. You may be able to find a cheaper set of spacers, but you really have to be careful with them and check them VERY often. That means you have to pull all your wheels and re-torque them which would get old after the first time (to me anyways). I'd rather know that my wheels aren't going to fall off.
here's a pic of my YJ with 33x12.5x15s with 3.5 bs steel wheels..
edit: wow that first pic got BIG