Nah... It'll be just fine. As you may know, some stands are made so you can rotate the screen. I know I've turned my old CRT on it's side before for a Dreamcast game. The screen slowly began changing to this pinkish color if I remember correctly. Weird stuff, but no damage done. Again, that was a CRT, not an LCD...
One thing that struck me, but shouldn't be a real problem...be sure it's well ventilated. As you know, heat rises, and most have vents on the top. If it's sideways or upside down, it may not get the cooling it needs.