Now this is a big quilt! It's the AIDS quilt in Washington DC. You can see a huge zoomable image here.
But I mean, what's the biggest you'll make? I was asked to make a quilt measuring 100" x 108" and I'm beginning to realize that it's not going to work. I think the biggest I can manage comfortably is about 60" x 75." My favorite size is about 50" x 50" or 60" x 60." I use my regular sewing machine, a Juki 98Q for piecing and quilting.