Hey guys,
I'm having this problem for really long time but just kept ignoring it. And now I really want to fix it.
So my forum uses the Chameleon Dark theme. The problem is that the browser won't use the background-size: cover setting.
And thanks to this the background image won't resize when you change the size of the window of your browser.
Example: When I load the website not maximized (half size for example) it loads the background image well but when you want to make the browse window maximized the image gets centered and doesn't cover the whole screen.
Here are 2 screenshots - when it's okay and when it doesn't use the cover setting:
PS: When I check the CSS settings with chrome's dev tools the background-size is crossed with a black line.