Upload & Sell: Off
Besides Fred already defined it. "A reasonable height and just let run off the end as needed." (paraphrased).
I am on a 30" screen, 2560x1600 and some of the panoramas in this thread run off the right edge by quite a margin, maybe 40%, when my browser is full screen. This completely ruins my impression of the image as a whole, since I can only see a small chunk of it at a time, and imagine how people browsing on 15" and 17" laptops feel. Other panoramas here are maybe 600 wide, just thumbnail size, unless you click on to another site. This means that I have no way to just scroll down and see various panoramas, one after the other. I have to click a bunch and scroll a bunch, and honestly, if a panorama doesn't have anything at 1200 wide, it just won't be effective on any screen, and should be put on a wall.
I think I will go start my own thread on getdpi with 1200 wide panoramas. I find that the presentation differences here totally ruin the experience.
Sorry to sound so harsh, but it is just the way I feel (for this thread only).