I think it would make a wonderful tree skirt, but if you want a table topper, I would cover up the black lines with black bias tape, matching ribbon or decorative ribbon that went with the colors. It's too bad the person donating the quilt did not notice the black lines before donating it. If you wanted to make it into a tree skirt, I would cut it between two blocks, then add bias binding matching the background color, or any type of decorative element. There are some great ideas from QB members, choose the idea you like best.