Here are some simple shaders for picom that give your setup an older look and feel. 

If you use these, I would highly recommend adding exceptions for some applications as they can be a challenge to use, especially with the monochrome (2 color) shaders (especially the posterized one). If you choose the monochrome shaders, I would recommend the dithered version as the posturized version will overexpose your desktop and make it a usability nightmare. The other shaders (EGA, VGA, and 256 color) are fine though.

To use them, set up your picom.conf like so:

backend = "glx";
window-shader-fg = "(PATH)"


Where PATH is the absolute path to the shader file. For instance, /home/user/Documents/ega.glsl.

The monochrome shaders are made by PickNicko13 and modified to display monochrome. Here is the link to the original project: https://github.com/PickNicko13/picom-o8dither