Not all icosahedrons have to be dice. A cube-shaped pie wouldn't be an "edible d6." Okay, I guess it could be...
I guess my point is that icosahedrons are awesome shapes that have myriad practical uses outside of D&D. For example, icosahedral viruses can be used in biotechnological applications and icosahedral structures can be used in architecture. So there are plenty of things that an icosahedron could bring to mind aside from gaming dice. But if that's what image means to you, I guess that's okay too, nerd.