I've been dealing with this issue for about a year now with my 15" MBP Late 2008 Unibody and think I might be able to help.
There are two potential causes with this issue (well, three if you count a wonky LVDS cable connector on your logic board), but the two that are economical to fix are: 1) a broken/pinched LVDS cable, or 2) a broken connector/circuit on the LCD panel inside your display assembly itself.
I was having this exact same issue with my display since January 2011, however I have no physical damage on my MBP (externally, at least). I found that when I was rendering in FCP or After Effects, the additional heat generated would expand some parts in the display assembly and wonkify my video signal, just like your picture shows. I could get the signal back if I pushed on the back of my display assembly, about half way between the top and bottom, and halfway between the apple logo and the side of the display. The problem would sometimes go away for a couple hours or days, but would always end up coming back when the display heated up.
I managed until last October before breaking down and searching out a fix; the problem had become so bad that I needed to squeeze/twist the display all the time to get the display straightened out. At the time, there was nothing on the internet to help diagnose the issue and point me in the right direction, so I winged the repair, hoping that it was the LVDS cable and not the whole display panel. I ordered a replacement from HK (not from iFixit; I found an OEM part for less elsewhere on the internet, but I STRONGLY recommend getting your parts on this here website!) and set to the task of disassembling my entire computer and peeling the display assembly apart to replace the LVDS cable.
I would consider myself a very skilled repairmonkey, but getting the glass away from the display frame with a heat gun was probably one of the most harrowing things I've done this side of jumping out of a plane. After, the cable replacement went smoothly (be careful not to pinch or sever the new cable in the replacement process!) and everything was back together, I was in the clear! It seemed like the LVDS cable replacement had done it, and for a week I was proud of my handywork! That is, until the wonkification returned.
After a surprisingly helpful trip to my local Apple Store, a well-versed Genius and I agreed that if it wasn't the LVDS cable, it was definitely the cable interface or circuits on the LCD panel itself. The area where I was pushing the display to make things work is exactly the location that the LVDS cable connects to the LCD panel inside the display assembly.
So that's where I am right now. I just ordered a replacement LCD panel here and I'm waiting for FedEx to drop it right off. I'll update when I'm done to let you know how it goes, but I wanted to post some notes for the other intrepid iFixers out there with some warnings:
1. This is an EXTREMELY INVOLVED REPAIR. If you're not comfortable using a heat gun on your computer, or if you're squeamish peeling the superthin glass display front off your display assembly, recruit a friend or reconsider your options.
2. If you're going to the trouble of replacing the LVDS cable and front glass, I would go ahead and do the LCD at the same time. You'll kick yourself (like I am doing) if you need to get back in there a second time, and a new cable, new glass, and a new LCD panel is still cheaper than the ~$600 CAD part cost quoted by Apple to replace the whole display assembly.
3. Be very delicate with the black rubber band around the display when you're using the heat gun and spudgers to get the display glass off; any nicks in the hot rubber will stay. Also, if you can, make sure you have a little bit of fingernail so you can pry on the thin metal edge of the bezel with your fingertips when you're pulling against the glass during removal; otherwise you'll find you won't have much leverage to pull against when you're peeling the glass off.
4. Watch the clutch positioning cover during replacement; you need more force than you think to snap the retaining clips back on, but you can still crack the clutch cover if you don't have the tabs properly aligned on repair.
That should about do it! Good luck on your repairs, I'll let you know how mine goes, and PLEASE UPVOTE THIS RESPONSE if you think it's been at all helpful!