How: bottomless pit of Darkness??

Here's a typical dungeon thing that is stumping me due to the premade map I am using. The map is really perfect for what I need, the place I envisioned, including having several half-broken rickey wooden bridges... which I want to be over deep deep maybe bottomless pits/depths. Now, if I run DL along the sides of the bridge, PCs see nothing. Not exactly the affect I am going for. I could leave it visible off to the side of the bridge, problem is: the map designer made the map background gold-yellow. So leaving visibility to the sides of the bridges shows not darkness, but gold-yellow... area. Any clever ideas on how to show dark bottomless depths to the left and right of the bridge?? (obviously at some point I will drop DL so they can't see anything further than their darkvision/light source would allow)

Off the top of my head? Fix map in GIMP. Should take a few minutes at most, if you're having trouble with it please feel free to PM me and I'll alter the map for your needs. That said there may be some more clever suggestions along shortly from wiser heads than mine... 

Why not just draw solid black rectangles over the map?

find a picture of darkness (black ssquares like Vince suggested, pit image, etc) and put it over the bridge area.  Then grab an image of a bridge and put that over the darkness.

I might try adding a fading texture around the outside.  For fun, I made this one (Russ Hapke looking over my shoulder and saying "yer doin' it wrong!" the whole time!). Here it is:

The Aaron said: I might try adding a fading texture around the outside.  For fun, I made this one (Russ Hapke looking over my shoulder and saying "yer doin' it wrong!" the whole time!) Here it is: yer doin it wrong, Aaron... [heehee], Oooo...that repeats well! Sweet! Yer doin it right, Aaron! haha Looks great!

You guys are goooooood. Thanks for all, now to play around and see... :)