This follows on from the Halloween card I made the other day and uses a plain brown lunch bag (10 for £1 Home Bargains etc.) and the Halloween paper chains I found in HobbyCraft (120 for £1).
All I did was make a front and back panel for the bag by sticking four paper chain strips side by side on a piece of scrap paper and trimming them down to size, and then mat and layered each panel on black paper. I added another strip across each panel that said Happy Halloween, and faux stitched, using a white gel pen, around the black matting and across the middle strip to make the panels “pop”
I stuck the panels on each side of the bag, folding them across the crease of the bag so that it could still be stored flat and then, in the spirit of Halloween, hung two spare plastic ghostie novelties on a short length of cord, threaded through a hole punched in the handle of each side. 
So, if I was having a Halloween party, for just £2 I could make 10 really cute bags …… adding a novelty or two would only add another pound (packet of assorted Halloween novelties £1 Poundland) ….. much cuter than a printed plastic bag and taking all but a few minutes to make each one.