We're fans of carpet tile in general. Shaw's EcoWorx is our favorite, combining non-vinyl chemistry, lifetime recycling, and a pleasing low-sheen appearance. But, if you're not a professional designer, it can be as hard to source as Shaw's website is to navigate.
FLOR has always been accessible and green. And their wool fiber options (the backing is still vinyl) make it an even better choice.
Two styles, Counting Sheep and On the Lamb, (wittily named as ever) are available in a range of soft, natural tones. Cost is a step up from other FLOR products: $17.99 to $19.99 per tile. FLOR says these tiles are suitable for light traffic.
If you take the plunge, check out our post on how to install carpet tile.