Need CCS code for that

Homepage message bg-color to black/transparent

Your version is phpBB3?

Yeah...

Add this to your css stylesheet:

Code:

div.panel introduction div.inner{
background-color: #color;
}

Or for image:

Code:

div.panel introduction div.inner{
background-image: url(linkoftheimage);
}

Nothing happened

Do you changed #color with your color? Try - http://www.colorschemer.com/online.html
For black change #color with #000

Yes I did...

Try:

Code:

.inner{
background-color: #000 !important;
}

This may work:

Code:

.panel.introduction {background:black;}

Oh, shame for me. The div's class is "panel introduction", so space between in css is considered that a other tag name, class or id.