I had never tried this, so I did the following:
With FTM 2005, I chose "Descendant Tree - Standard" with the option "Direct descents from William Marshal to Ella Frances Miles" (my grandmother). Under Format, I chose custom layout, automatic. I also selected a nice border and wrote a title. I just chose to put the name in each box, no dates, etc.
Then in FTM under File, Print Setup, I selected "Specific Printer" and "Microsoft to PDF" and chose 0 for all margins and deselected overlap pages.
With the information about medieval people that I have currently included in my FTM file, my grandmother has seven descents from William Marshal (one from Isabel, four from Eva, and two from Maud). The tree fits on 4 pages with the above options.
Then I selected File, Print Descendant Tree. (I am using Windows 10, the Export the Descendant Tree to Acrobat (PDF) function in FTM 2005 does not work on Windows 7 and later. Choosing it crashes the program.)
Then I used the website http://pdftoimage.com/ to produce 4 jpg images of the four pages of the pdf.
Finally I used IrvanView (from http://www.irfanview.com/) to stitch the images together, using the Image, Create Panorama image command. I did this by creating a horizontal panorama from images 1 and 2 and a horizontal panorama from images 3 and 4. Then I created a vertical panorama from the two horizontal panoramas. For each panorama I chose -1 pixels as the space between the images because with the default 0 pixels, there was a little gap.
I think the final image would be good enough to hang on a wall but printing a legible version would require a printer that accepts large paper. I suppose one could print it at a print shop that had such equipment.
There is one odd thing about the Descendant Tree made by FTM 2005. The line to each descendant goes from the spouse of one descendant to the next descendant instead of from the = sign that joins the spouses.
Jordan, I'll send you my jpg file so you can see if you like the result well enough.