There's not a quick way to export your family tree as a JPEG. You can print your family tree, cut two of the edges, and then tape the pages together. I did that the first time just to see what it looked like. It works okay, but I had a l little trouble printing it big enough. I wanted something to take to our family reunion too.
There are companies that will print out your family tree for you from your GEDCOM file. This resource lists a few of them toward the bottom of the page. Note that your GEDCOM file doesn't include pictures.
I actually purchased Family Tree Maker just to use their charts. I work in FamilyEcho and then export my GEDCOM file and import it into Family Tree Maker. They have an option where you can print out your whole family tree (subject to the normal limit of how much of a tree you can realistically display at a time) as one large PDF (instead of splitting it into multiple pages. But there is a limit to PDFs of a maximum width of 200 inches (about 17 feet), so there are some compromises there as well.
After I had my 3 feet by 17 feet pdf file, I had to find someone to print it for me. If you go this route, I found that blueprintsprinting.com was pretty reasonable at about $45.00. Office Depot and places like that can print that large as well, but they wanted much more money. After it came, I took shipping tape and taped the backside of the family tree so it couldn't rip. I might laminate it eventually, but I figured people would point out errors in this first one.