hi , this is abt my yabb forum.
Below is a part of colors section of Settings.pl

$color{'titlebg'} = "#6E94B7";                                        # Background color of the 'title-bar'
$color{'titletext'} = "#FFFFFF";                                      # Color of text in the 'title-bar' (above each 'window')
$color{'windowbg'} = "#AFC6DB";                                       # Background color for messages/forms etc.
$color{'windowbg2'} = "#F8F8F8";                                      # Background color for messages/forms etc.
$color{'windowbg3'} = "#6394BD";                                      # Color of horizontal rules in posts
$color{'catbg'} = "#DEE7EF";                                          # Background color for category (at Board Index)
$color{'bordercolor'} = "#6394BD";                                    # Table Border color for some tables
$color{'fadertext'}  = "#D4AD00";                                     # Color of text in the NewsFader (news color)


now for eg. what i want to know is how to get a image in the background or the titlebar instead of a simple color(like boardmod).

Thanks in advance

Curtiss, you are correct.  The changes need to be made in the CSS portion of the template.  For example:

.titlebg   {background-color: #ffffff; background-image: url(http://www.yourserver.com/pathto/image.gif);} 

Yes, it does.  The colors that are in the Settings.pl are only for browsers with non-CSS support.

FYI, once you have uploaded your forum, you will be able to change those colors (the ones in your Settings.pl)  from the comfort of your admin center, under forum preferences and settings.