I first saw the idea a few years ago on one of my favorite blogs, Filth Wizardry. Back then, my kids weren't even interested in Star Wars, but I kept it in the back of my head. The link in her blog didn't work, but I was able to google Star Wars masks and found them on starwars.com. They have several sets of masks to choose from, I chose characters that I knew my kids would like.
I printed the masks onto cardstock, then I hot glue gunned on a headband or a pair of sunglasses, instead of doing string to tie in the back. It was much easier to put on and take off, especially for kids. I got that idea from the Filth Wizardry blog- pure genius! Also, if you do use sunglasses, kid sized ones might be too small for kids over age 7.
Check out the star wars site if you're looking for party ideas or just for some masks for a fun day playing at home. When you print, you should be able to go into preview and resize the masks to fit the page. I had to adjust them all to print out in full on the paper.