Silver halide crystals come in virtually every geometric shape including cubes, octahedra, pyramids, and etc. The pAg at the time of manufacture governs the form. I describe this in my book.
The developed silver can be in the form of filaments, tablets, and a variety of other shapes depending on the developer. This is shown in Haist for example, with photomicrographs.
So in a way, yeah, films have squares! Only they are better, they are cubes.