It gave me an idea, so I had a go at making one myself.
Screensaver - 55.3mb, self installer (Xvid codec required)
Download from Guild Wars Guru - Thanks to the GWG team for hosting

Download from Filefront
- Run the Screensaver installer, this should bring up the Display Properties after installing (if it doesn't just bring it up yourself)
- Select "GuildWarsPanorama High Quality" screensaver, and adjust the settings to suit. From here you can add your own music playlist, change the size of the video etc.
- That's it! Preview it, or let it fire up like a normal screensaver.
- If you get a black screen, you probably need the Xvid codec. Get it from here http://www.koepi.org/xvid.shtml The "latest stable binary" near the top.
- To uninstall, you can remove it from Add/Remove programs or the Start menu under Programs.
The full rotation takes about 10 minutes, I couldn't get a perfect seam at the loop due to the animated water but it's barely noticeable. The video was recorded at full detail, with 4x Anti Aliasing. You might need a reasonably fast machine to enjoy at its best, not too sure. For reference, my computer at the time of this post has Windows XP, Pentium 4 3ghz, 1Gb memory, ATI Radeon X800. Some free advertising for GWG in the credits hehe
Music (optional)
For those who like the intro music, here it is

Intro Music mp3
You can add that to the playlist of the screensaver and it will be more or less like the ingame intro then, just lower quality.
Enjoy!
Xen
Update: The new updated screensaver should have options like this:
If yours has no such options, you have the old (discontinued) DivX version. Grab the new version instead!