I hesitated before answering, but I don't think black should be an issue as long as it's not a huge percentage of the top. I've seen some great black and white baby quilts, too. Black can often make bright colours pop more, so it could actually be great for the quilt, depending on what it's paired with. I guess, as usual, context is key, so my final answer would be "I don't think it would be my first go-to, but I wouldn't avoid it if I thought it would work with or enhance the quilt I was making." :-)