I love the limestone look as well and have used lots of it but I might ask a few questions first.
One is how you want the tank to work as far as PH/GH/KH. Since limestone does run those readings up if you add it to water that is low in any of those. Not a problem if your water is already hard and alkaline but something to consider if you have soft acidic water.
Second is how much effort versus how real you want the wall to look. Also something to consider is how much art skill you have. Art to make a fake look real or mechanical skill and tools to work the real rock?
Cutting, fitting and attaching real limestone can turn out great but it is also a long, challenging process!
I do not advise fitting rock directly to the glass as scratches are almost certain.
That leaves many making a fake which is "okay" but not the real good look they wanted. It's hard to fake natural stone. If not into the real, I suggest looking at foam covered with something like quik-crete, etc.
Maybe do some searching for walls and how to?