Well, it isn't quite perfect yet, but I was inspired by @Bauke and their fantastic Dracula theme and ended up losing the better part of my afternoon making a dark, terminal inspired theme I call Terminally Ilios. I think it's pretty easy on the eyes and looks especially nice at night. Screenshot. I'm just running it through Stylish, let me know if anyone finds any oddities.

Some minor Stylish tweaks:

p {max-width: 95%; text-align: justify;}
blockquote { max-width: 92%; }
#sidebar {min-width: 250px; width: 250px;}
body .post-button-used {color: #FF8C00; }
.btn-used { background-color: #FF8C00; color: #FFFFFF; }
.is-comment-mine > .comment-itself { border-left: 3px solid orangered !important; }
.is-comment-mine > .comment-itself > header { background: gold !important; }

Most are geared towards widescreen use (p, blockquote, #sidebar). The vote buttons I've made orange if I've already voted. The original blue vs a slightly different blue wasn't clear enough for my eyes.

Own-post highlighting (.is-comment-mine lines) I stole and modified from here by @tomf.

Not really a theme per se, but here's my Tilde colorscheme. I override all sites with these colors to make them more ergonomic and blend in with my desktop theme better, which looks like this (for context. And if the pictures look blurry, that's imgur messing them up, try right clicking and selecting "view image", or if that doesn't work try downloading and viewing them in your native image viewing app. The text especially should look razer sharp and clean, and at 1280x768, it's unlikely you have a lower resolution then I do :P ). If you want to replicate this yourself, using Firefox, just go to preferences, search for "colors", and set text to black, background to #DCDCDC, unvisited links to the third box from the bottom of the black / white column, and visited links to the bottomost square in the yellow / orange column. (the fourth column from the left). It's very plain and sometimes breaks sites that rely on custom color / fonts, but it's so easy and comfortable to read that it makes it well worth it.

Very much a work in progress, but here's my attempt at a nostalgic terminal/CRT style theme for Tildes:

https://gitlab.com/snippets/1721975

Screenshots:

https://i.imgur.com/scwKpAX.png
https://i.imgur.com/ArtwT6w.png

Using Stylish, I've only added a few things

.topic-full, main, .post-listing {padding: 60px 0.4rem;}
#site-header {position: fixed;background: #002b36;min-width: 100%;border-bottom: 1px #AAA solid;padding:10px;z-index: 99999;}
#sidebar {padding: 60px 0.4rem;}
.is-comment-mine {background: rgba(255,255,255,.5);}

nothing crazy. It makes the header static and highlights own-comments. My CSS is rusty, so there's probably a better way to go about this.

Commenting so I can come back later and install these (wish there was a save feature haha)

Oh well I didn't know so many came up with their own theme.

I don't have a theme but am writing an extension for tildes (search "tildes extended" for Chrome or Firefox) and was just thinking this morning what could I add to it.

An interface to load CSS, given an URL provided by the user seems quite interesting.
I'lll work on it after lunch.

I already commented below, but I figured you might be interested.

For the username mentions alone I am using body a[href^="/user/"]:not(.link-user):not(.logged-in-user-username) {color:#FF79C6!important}