You might consider creating a bluestone walkway. Consider bluestone of all one size, rather than random sizes. This way it won't fight with the travertine pattern. Eighteen inch or twenty four inch squares would work. If the walk turns out to be curvilinear, the edges should be saw cut to make a beautiful curve.
I think this would be a nice transition, as the bluestone walk should go well with both the existing travertine patio and the stacked stone fire pit.
