Remember to take into account the other colors used in the miniature. Colors on shiney new leather would be reflected from the surrounding colors, and brown can be used to represend worn areas.
Like if The make colors were like a red or rust color, then something like a dark flesh, or vermin brown highlight would be nice. You could highlight with grey and then glaze it with a different color, to lean the color toward the surrounding colors.
Also remember that black isn't usually true black in real life, so another color glazed into the shadows, like was mentioned would also be very effective. A mix of Scorched brown (which is a burnt umber) and ultramarine blue (which is the actual color, not the color of the ultramarines) is used as a very nice "mixed black" by a lot of painters working on canvas, and can be very good for a shade color.