I had a new shower/bath area built and plumbed quite some time ago. I have finished tiling and an ready to have the shower nozzle, hot/cold knobs, and bath faucet installed. I was just told the pipes that were installed must match the brand of fixture. Is this right? I have no idea what the plumber's name was or how to ask him if he plumbed for "moen" or Price Pfister" or what.

Can anyone please help?

If you are at the stage that you have tile on the walls you already have a faucet in the wall, and you or the plumber that installed the faucet should have the rest of the parts needed to finish the job, it is called the trim package. There are some situations where the plumber only buys the faucet body but not the trim package. Then he buys the trim package at the time the jpb is going to b efinished out. My sugestion to you is to either call an independent plumber and tell him what you problem is and see if he will come out and tell you what faucet body you have. If he can then let him finish the job for you...
Good Luck

Things must work different in Letmetellu's area then in mine. He was entirely correct when he told you that if the shower walls were tiled then you already have a valve installed. I guess it might be possible to purchase a valve without the trim but I've worked all over the state and never worked for a shop that didn't stock the complete package. Nor have I ever found a wholesale house that sold them that way.
I think what's happened here is that the shower was plumbed the tile went in and then the job was left setting for so long the plumbers name who had the trim was lost.
Follow Letmetellu's advice and call in a plumber to see what you have inside the wall. Once you find out the brand and model name you can began to chase down the trim. I have never purchased just the trim package from a wholesale house unless they were willing to break open a box and rob one but I imagine one can be ordered direct from the factory. Good luck, Tom