Brown leather is such a dominant feature in a living room that it must be taken into consideration when decorating. Brown isn't a hard colour to coordinate, although too much brown in a room can become drab and tedious. Keep your options open, and look to other natural--but masculine--colours.
Sage green, another earthy colour, is appropriate when placed against medium-toned brown leather furniture. Choose a sage green that has a hint of grey to help the green recede into the background and showcase the rich brown leather furniture.
A light, warm beige, when accented with trims of cream or white, will work with brown leather--a little too well, maybe. In larger rooms, that much beige, combined with the leather, could be just too much brown. In that case, a beige accent wall in a room of cream-coloured paint is a smart alternative.
Pewter grey is a sophisticated colour choice. The coolness of the neutral grey contrasts just enough with the brown of the leather to create a well-balanced, coordinated colour scheme. If you're worried about the room becoming too dark, paint a cream accent wall.