One inexpensive Halloween decoration with high impact is homemade window silhouettes. I made mine a couple of years ago using silhouettes I found online and then I used Visio to enlarge the silhouettes and print them out to fit my windows. The silhouettes were printed out using several pieces of paper that I cut out and then I pieced them together like a puzzle to make each silhouette. I then backed each image with pieces of tissue paper. Once I attach the silhouettes to the insides of the windows using painter's tape (this type of tape holds strong but comes off cleanly), all I need to do is wait for night to come and then I turn on the lights -- the silhouettes show through wonderfully!
To make the images stronger, this year I "laminated" the silhouettes using packing tape. After Halloween celebrations were complete, I stacked the images from a room and rolled them up together for storage in my attic.
I love the effect so much that I will make some more for next year's pumpkin carving to cover a window in my house that has an unsightly view. During the day, the sunlight will "turn on" my silhouettes and add some Halloween spirit to the room!