First I took an expo marker and drew the basics of what I wanted space wise straight onto the glass. This proved to be a great way to begin.
Next, I put the poster board up against the window and traced out the shapes in pencil. I did this in the daylight, so the expo marker was dark enough to see through the poster board. I cut them out, then went over the edges in black marker. The suckers were added (in sharpie) afterwards, once I was sure how they were going to fit on the window. Once everything was in place, I taped everything securely. I also did marks (outlines and suckers) on both sides of the paper--just so that it would also look cool from the inside as well. I'm also thinking I'll hang some of the homemade seaweed/kelp over the pumpkins, just to give it a little more depth.
The next big test was to make sure that the paper lit up under black light. I pulled out a black light bulb, put one into the new three way socket and hung it roughly where it will eventually be. The paper lit up very well.
Pictures aren't super obvious how much the paper lit up, but they looked great:)