Ok, so I did a rough mock-up with some open source images/icons and a little bit of CSS.

https://imgur.com/a/wwOXLW1 (These screen shots have the page magnified to show the icons better)

The changes I made were:

• Changed the Insightful and Fun icons to something cleaner and aesthetically similar.

• The light-bulb (insightful) lights up when it's clicked and the smile (fun) winks when clicked.

• Both icons turn orange when they are active.

• Visited links are orange instead of dark blue, this makes it easier to see on the (default) dark theme.

• Changed the top banner on the homepage to a blurred CC image of a nebula, and made it cover the full width regardless of window size.

This is just a rough proof of concept, but I'm excited to see what people think. I work as a web developer and while I've never touched the saidit or reddit code bases I think I could manage a PR.

Edit: You can try these changes out by applying this CSS as a user style. I used the 'User CSS' browser plugin to do this.

#header{
  background-image:url('http://138.68.219.81/img/saidit/banner.jpg');
  background-size:cover;
}
.arrow.up{
  background-image: url('http://138.68.219.81/img/saidit/light.png');
}
.arrow.upmod{
  background-image: url('http://138.68.219.81/img/saidit/light-set.png');
}
.arrow.down{
  background-image: url('http://138.68.219.81/img/saidit/fun.png');
}
.arrow.downmod{
  background-image: url('http://138.68.219.81/img/saidit/fun-set.png');
}
.thing .title:visited, .thing.visited .title {
  color:#ff7500;
}

The images are temporarily hosted on my personal server.