Question about making a wall size mural print
Look for a digital lab that uses 3M Scotchprint adhesive backed media and has experience with wall mural installations.
Larger murals are usually prepared as single file. The lab's rip software will divide it up into 4' sections for mounting. A 12 ft wide x 8 ft high wall mural would probably be printed in 3 - 4' x 8' sections. It is tough to handle paper wider than 4'.
The paper manufacturer publishes wall prep specifications that the lab can give you. Basically the wall should be clean, smooth, primed and dust / bump free. Defects in the wall or imperfections in sanding etc can show up in the finished product so the standard for wall prep is higher than what a commercial drywall finisher's usual is asked to do.
Costs vary wildly and specific installation requirements and site logistics are a big part of it. A center city office building could require cooperation of a couple different labor unions and building maintenance staff. Talk price with your printer and give him as much detail as you can. You will probably want a single supplier to be responsible for the entire job, printing and wall mounting. That way there is no finger pointing.
We always include an overall print for client approval and sign off plus a full size test section. This helps eliminate complaints after completion. Its a lot easier to retouch in the computer rather than on the wall.
Good luck with your mural.