I've had many photos from trips blow up and depending on the resolution, you can go pretty big. I've worked with a guy in the Tremont area of Cleveland, Paul Duda
http://www.pauldudagallery.com/.
He is great guy and the prices are very reasonable. He has some giant panoramic shots of the stadiums in Cleveland and the skyline that are impressive. You can e-mail him a photo and he'll tell you how big he can make it. I've used him many times and highly recommend him.