yes definitely rug or else it will look too industrial like a work space. i would do an off white if its not high traffic with gray undertones or designs to warm up the space. something along the lines of this. lower pile than last photo so not tripping hazard

this could work but as long as it's gray and not black squares which look too intense

Get a rug.

Another vote for a rug. I’d keep it low ... natural fiber or handloomed:

matchy matcy one from rugsusa

Some more natural ones