Minor visual changes (that should be noticeable in dark mode)

[DaFace]

Just so people don't freak out, we're making some minor updates to a lot of the icons on the site, courtesy of Armyofme. He saw people talking about our shitty icons in the thread about dark mode and volunteered to help us get some things updated.

Most of them will look like better versions of what we had before, but you may notice a few icons changing to something slightly different. Just wanted to give everyone a heads-up.

(And say thanks to Armyofme for the work!)