These are all shot against a green screen - 9x12 - lit with 5 lights. Key and Fill, two background lights to get a uniform light exposure on the green screen - and a backlight to create an edge separation from the green screen. My studio is 20x30ft. - it's the space above my garage. It has a 14 foot ceiling so I can get the lights high and spread the subjects out (away from the background) to eliminate any green splashes of light.
Once shot, I pull the images through camera raw into PS and drop the green out. I have done several images where the guitars are arranged in a certain way, like you'd arrange during a product shoot, but they were shot at separate times. I always shoot guitars the same way. The same height etc... setting on my tripod. So I always have a uniform viewing angle.
If I want to place the guitars closer in the images, a little drop shadow on the guitars in the rear makes a world of difference to your eye. Your eye is tricked and you don't question, unless you are a photographer and are looking for it, that this is a real setup.
I then create - and have created - countless plates - colored backgrounds, textures, etc... that I can use to create the backdrop space.
It's much easier than dealing with flares, strange artifacts, and on dark backdrops - which I do own - I have to constantly clean the cat-fur off of them. LOL.