I purchased eggshell finish by mistake instead of flat (which my other living room walls are). Will it look odd to have one wall with eggshell and the others flat?
There is a big difference between an eggshell finish and a flat finish even if you have the same color. The difference is very obvious too. Almost everyone is able to spot the difference if they pay relatively enough attention to it. You can have different finishes in different rooms, but definitely not in the same room.