That doesn't invalidate GP's points. A collection of B&W icons with similar base shapes (circle, square, rectangle) and no contrast is terrible for using the in

That doesn't invalidate GP's points. A collection of B&W icons with similar base shapes (circle, square, rectangle) and no contrast is terrible for using the interface. Each icon needs a distinctive element, be it color, weight or shape, to make it stand out from the other icons near it. If you're designing a B&W icon set, at least make sure that each one has a very eye-catchinge, different outline.