The landscape materials used in this photo is a Dark mulch, with black aluminum divider. The 5/8 clean gravel for the pathway is place in between 2'x2' Paver stepping stones
Installation of river rock allows for lower maintenance. River Rock will not need to be replaced every 2 years like mulch. The grass is separated by a 6"x9" charcoal paver to define the edges. The rock is great for accent in those area's where you could see excess water.
Large Boulders are a great way to add character to the landscape. You do not have to replace, water or do anything at all once they are placed. Placement of large boulders can allow a sloped area easy to landscape with out putting in a retaining wall. Great for a NW landscape theme.