Just as natural backgrounds make a big difference, backgrounds you choose have a big effect. We had Nicole hold her pose while our daring intern Mike flipped new backgrounds in and out at blinding speed. This is one reason we didn't use commercial backgrounds — they are too large to flip in and out that fast. Plus we didn't need large backgrounds, so art-store paper was cheaper and easier.
Bottom Line: if you can, choose your backgrounds so your subject resonates nicely with them.
100mm, f19, large studio softbox on left, reflector on right