I strongly disagree with this suggestion. For someone not familiar with all the textures, 2x2 icon gives a much better idea of what it will look like when applied than 2x1 icon where you look at the pattern from less than 30 degrees angle.
As for space, there is enough space in a shopkeeper for 20 2x2 icons; containers can indeed be a pain sometimes but I guess lobbying for resizable container windows might be a better idea.