The blue and ivory in your current rug already give you a useful starting palette. If you're replacing it, I'd look for a muted denim or indigo pattern with warm sand or ivory, rather than a mostly white rug or a very cool gray-blue. That should connect the light sectional to the stone fireplace and dark ottoman without making the middle of the room feel washed out. Before ordering, bring home a few swatches and check them beside the sofa and fireplace in daylight and at night; rug photos can shift the blue and tan quite a bit. Also tape out the candidate size so the sectional's front legs and the chair can both sit comfortably on it, with a visible border beyond the ottoman. Would you prefer a quieter pattern than the current rug, and what size and budget are you considering?