Wrinkles are the one thing to avoid.
Paper is a good choice. I also like PVC sheets, they are often more matte and more durable.
If you want a canvas, I strongly suggest getting one which can be stretched, instead of muslin. I have a black backdrop, I got it from B&H and believe it's this:
Westcott 9 x 20' Wrinkle-Resistant Polyester Backdrop 138 B&H
I use cheap clamps to hold it stretched by clamping along my vertical posts. It creates a clean, uniform and wrinkle-free background in seconds. I've seen photographers use heat and vapour to remove wrinkles with little success, using a stretch fabric is much simpler.