really the only carpeting plant that will do well in that kind of light would be some sort of moss, i would recommend flame moss, or fissidens fontanus. both can/will carpet if given a long time to grow. They also do well in lower light tanks.
sometimes microsword will do ok and sometimes glosso will do ok in those conditions but in my experience its always easier/nicer/cleaner to just use a moss.
On a side note if you want to keep your plants very pristine and clean of algae and waste, look into getting cherry shrimp, they are easy to breed and keep your plants looking clean. But this is of course if you weren't planning on having any fish in there.