Pretty please
Remove the dark theme image transparency for all images (pictures, flags, smilies, etc.). It doesn't help with visual comfort and the images look drowned.
The lateral background is dark only up to a certain height of the page. Then it's again white. Please fix.
Stick to neuter grays for backgrounds. There's enough blue light already from the display. Maybe try some light orange for color accents, instead of blue.
Current font doesn't look as good on the dark theme as on the light theme. Maybe you could find a better one. Look for "display fonts".
Thanks!