Blue Star Creeper - Isotoma axilaris
Blue Star Creeper makes everything around it look good. A sweet little filler, it looks like a moss with tiny blue flowers, but it's surprisingly tough.
Year two, it puffs up to about 6" and the flowers become 1" lavender-blue stars. Laurentia spreads through underground runners. It may disappear in winter, but it's still there. Over time, you'll have a full patch of starry fluff .
The seeds are expensive, not for random broadcasting (unless you're very rich). Surface sow them in a pot till they're established, then transplant and allow them to fill in over time. Fill in they will. They're perennial in zones 5 through 9. Dappled shade with even moisture is ideal.