Since the boots are black, I wouldn't wear them with black - you've gotta be able to show off your boots! Dark Brown or grey woolen leggings would look good (very Sienna Miller)and I have also seen some funky colored leggings (grey purple, dark green etc) with subtle pearls and they would look cute too.. If you feel brave, you can wear them with a little pleated skirt or A-line skirt.