The easiest answer is whatever you like or whatever you have. I am a reborn child of the depression. Right now, that is a great thing. Hopefully what you bought for future projects (our stash) is still what you like. If so then you have SCORED! If not, please take a look around our site to find new fabrics that you will love.
Most quilters like 100% cotton fabric like printed quilting cotton, shirting (homespun), batik, or flannel. Each of these start off as a pristine sheet of greige fabric. The higher thread counts the better. Most of our quilting fabrics are from top line vendors. They use what is called 60 square greige, a very high-quality base.
Printed cotton is typically what everyone uses. The colors and patterns are rolled or printed on the top of the fabric. While in shirting each of the threads are individually died and then woven together. Makes it less likely to fade. Batik is a type of resist printing process where wax is applied to fabric in specific areas.
Be careful when buying from a “big box” store. Many times, you will see the same designs that quilt shop carries. The big difference is the thread count. When manufacturers start the process of manufacturing “runs”, they use a much lower thread count or greige fabric which they sell to the chain stores. You can tell by the feel or hand of the cloth or if the design is printed straight. Also, you can rub the fabric with a white cloth to see if the print comes off on the white.
The biggest NO NO in quilting is to never use a bedding sheet. The fabric is finished such that the needles have a difficult time piercing. This will result in missing stitching and picking of the threads.
Hope this helps with any confusion of what quilting fabric should be and makes your quilting experience a happy one.