It's called "Knockdown". It's rather easy to put up.
Go to your local Rental Depot and rent a Knockdown Gun. If you dont own a compressor, you'll need that also. They sometimes sell the mix you need as well. You'll also want a paddle for your drill to mix it with, they're cheap. You will need a big mud knife as well, like 12''. Mix up the knockdown in a 5 gallon bucket, it comes as a powder so mix it to just a little to just under spackle consistency, this is the hard part. Start with small batches till you get the knack. Test it out on a big piece of cardboard. Theres a hopper you pour the knockdown mix in on top of the gun and a little knob on the side of the sprayer that regulates the amount of material that gets sprayed. You will also want to play with this to get the desired application. Again, test it out on the cardboard or spare piece of drywall. What you're looking for is little bubbles on the wall no deeper than 1/8''. Spray on the whole wall in 4-6' sections then come back and knock it down with your mud knife in random circles. You want to give the mix time to just set up a little. Then come back with your mud knife and knock it down, spreading it flat. Thus the name. If you dont give it enough set up time it will just smear, too much time and youll just have a bunch of little bubbles on the wall. If you mess up, just let it dry and pole sand it down. You cant really screw up, just cause yourself more work. It's a messy process so use plastic dropcloths on everything you dont want ruined. When you're done, let it dry and come back and paint over it as normal.
You can rent the gun for like $15/day the compressor is a little more expensive. The mix is like $10/bag I believe. I painted and fauxed for years so I did this a bunch. It's actually pretty enjoyable to do, IMO. If you want a nicer, similar finish, I love venitian marble. You will need a course from Home Depot or an experienced faux artist for this though. Let me know if you have any more questions.