1. Print out an 8x10 of the photo and trace the key elements of the photo onto acetate, then use an overhead projector to project the drawing the size you want it, and trace that image onto butcher paper to become the master pattern.
2 . Take the line drawing to Kinkos and have them print it out the size you wanted the finished quilt to be, knowing that the drawing might have to be cut in two or three pieces inorder to print out the size you wanted.
3. Save the photo on to a thumb drive and take it to Kinkos to have it printed in color ($$$$) the size you wanted the finished quilt to be. Again, the original might need to be cut in sections, enlarged and then taped together.
WELL, I've just stumbled upon a pretty easy way to enlarge a drawing to ANY size, without having to spend a fortune to buy photoshop. FREE (my favorite price, remember) software that can be downloaded from the net. Photos are converted into raster images (so there is no pixelation of the image, just the nice smooth lines, like in the original photo.) The software converts the raster images into PDFs, and you print them out on your home printer. You can chose the finished size of your enlargement by measurement, or by pages...for example 6 pages across, 5 pages high. There is an on-screen image that makes all of that very clear.
The pages need to be taped together, but since there is a predictable overlap, it's not too hard, as long as you don't scramble the order of the pages as they come off the printer. It would be nice if they had registration marks to make aligning the pages a bit easier, but it's not that hard really, unless a photo has a huge area of one solid color.
Printing the huge images in color is not completely free of course, since printer ink can put you in the poorhouse, so I've been converting images to B&W line drawings, as in #1 above, scanning the image and then enlarging it--a line drawing with 30 pages