I'm told that theming is in development, so note that this is a temporary measure until then. (Admins; I felt here would be best as users might look here to ask for a dark theme).

I have linked to a CSS file for plugins such as Stylish (exists for Chrome and Firefox), that allows the user to override the styles. I've tried to darken everything used in the forum; only very minor bits remain. If anything changes or isn't working, comment below and I'll update.

Stylish Theme: http://pastebin.com/tU5yz4Hy

Preview: http://imgur.com/a/ZqJ3T
(The very top line in the file informs the addon how to apply based on URL; the regex (describes URL) is "http[s]?:\/\/asgardia.space\/.\/forum\/." without the outer quotes (") ).

Stylish (Chrome): https://chrome.google.com/webstore/detail/stylish/fjnbnpbmkenffdnngjfgmeleoegfcffe?hl=en
Stylish (Firefox): https://addons.mozilla.org/en-GB/firefox/addon/stylish/ (If anyone comments with other alternatives I'll edit this post to include them).

Stylebot Theme: http://pastebin.com/5GbLR6uv

(Thanks FranklindAndrad)

Stylebot (Chrome): https://chrome.google.com/webstore/detail/stylebot/oiaejidbmkiecgbjeifoejpgmdaleoha
(Doesn't seem to exist for Firefox)

By all means, if you make your own variant, post it here (I might include it in this post).

Another option for chrome would be Stylebot in https://chrome.google.com/webstore/detail/stylebot/oiaejidbmkiecgbjeifoejpgmdaleoha

And the theme previously published adapted http://pastebin.com/5GbLR6uv

Thanks for the contribution, I've added it to the main post. :)

Thank you so much for the theme. Reading the posts is really unpleasant with the plainly white background.