I think the first one is the prettiest. Since it's a baby quilt I think I'd just do a nice SITD, or, if you want to get a bit more creative, do a cross hatch.... that always looks nice. I think I'd also add a small border or two..... maybe the inside one in white to frame it and then the outside one in strips of the colors that are in the blocks. I just noticed that in the second row from the bottom you have two yellow squares right next to each other.... you may want to move one of them around a bit.