Chad,
First of all, I want to say what a great job on your garage man!! Awesome!
We are doing our house in the REVERSE order that you got to do yours...
We've done every room in the entire house from ceiling, walls, fans, light fixtures, counters, bathrooms, wood floors, roof, HVAC, door handles..... Hell you get the picture..
Now I finally get to do the garage and I'm ready!!
You mentioned doing the synthetic stone on your wall. We did the same in our TV room and it came out great. We did this after looking at a few buddy's projects that did the same. One of them did a synthetic river rock all the way up the wall, similar to what you want to do with the stacked stone look. The stone is more like tile, goes on with adhesive, and you apply a grout material in between almost like you are tiling a floor. Now you are doing a stacked stone look (which I haven't done) but it will still be the same concept of appyling the synthetic stone (if that's the route you go) to the wall.
The attached pic is in my TV room which only has a 10ft ceiling, but my buddy w the river rock has probably a 20ft ceiling and it worked out really nice, gives and gives the look of a 3D fireplace all the way to the ceiling.
Both my buddy and I ended up sourcing large cedar beams and cutting them to the length we wanted w large circular saws. I then sourced a guy the could make the corbles to go under them, bolted them together from behind then bolted them to the wall with large lag bolts. (I could do pull ups on it so I know it was attached pretty well) In my case, we put it together like a jig saw puzzle as we had all different shapes and sizes. My buddies was river rock, so started at the bottom and worked his way all the way to the ceiling. With yours I would say it's start at the bottom and work your way up as well.
Attached is a pic of what mine, which I believe is called Austin Stone. I'll try to dig up additional info on the company that makes it. It's been a while, but I know when I looked at the catalog, there were several stacked stone options.
By the way your garage came out, I'm sure you'll do a killer job on the fireplace as well!!!
