Regular paper will work for many of the purposes that wax paper and parchment paper do. However, regular paper will absorb plasticizers from the clay, so you'll want to be careful about leaving raw clay on the paper for extended periods of time (unless, of course, you want to stiffen the clay). Any paper should do, but it's probably best to choose solid white, unlined paper, whenever possible, because polymer clay can absorb inks.