I already mentioned here a monochrome emoji set.

Here's another type of emoji set that I like: a pixelated-looking for/from SerenityOS.

In fact, I like the whole idea of SerenityOS:

SerenityOS is a love letter to '90s user interfaces with a custom Unix-like core. It flatters with sincerity by stealing beautiful ideas from various other systems. Roughly speaking, the goal is a marriage between the aesthetic of late-1990s productivity software and the power-user accessibility of late-2000s *nix.

We need more of the 90s, or even 80s!, aesthetics. It's a growing sentiment that I share with UI, and UX experts, who see the limitation of today's trends.