I need some fabric to make a 4 foot diameter hamburger for Halloween.
It'll essentially be 4 pillows (bottom bun, hamber patty, lettuce, top
bun).

I may just have to settle with a pale brown fabric for the bun and
brown fabric for the meat patty, but I'd prefer to find some fabric
that looks like it has sesame seeds on it and some fabric that looks
like it's hamburger meat.

I also need something to make some lettuce, but I figured I'd use an
xmas wreath for that. But perhaps someone has a better suggestion?

I'm also going to make an 8 foot hot dog, but I think a red velour
would probably look pretty good for that.

I was unable to find printed fabric, but for the sesame seed fabric I
suggest you try this: Spray the part of the fabric that is in view
with a spray glue, available at larger craft stores. WHile the glue is
dry, srpinkle real sesame seeds on the fabric, and press them lightly
with your hand. You could try this on a scrap first to see how the
seeds adhere.

Or,  you could paint on the sesame seeds as seen on this site:
http://www.hgtv.com/hgtv/dc_occasions_halloween/article/0,1793,HGTV_3475_1370945,00.html

http://www.funfolly.com/h/mascots/c1543.htm

Costumes for sale
http://www.brandsonsale.com/food-costumes-for-adults.html

Good luck!