If I make a material I am trying to market, part of my job is to show people how to use my product in ways they haven't thought of before, so my market size will increase. In the case of cultured stone, most companies have lots of project ideas and descriptions for their products.
Your framing should be stout, as cultured stone is considerably heavier than regular drywall or other interior finishes. Keep in mind that you are trying to attach the heavy stones to the surface, whatever surface you happen to choose to sheath the inside of the wall with (I recommend hardiboard, but that's just me.)
I can't give you a lot of other suggestions, haven't done one myself. Do consider hiring a plumber who is licensed in gas work to do the gas line, and consider a gas insert, as these can be much more efficient and effective at creating actual usable heat. Some brands are very attractive.