That's usually just the regular board logo that shows on every other page as well.
You haven't said what style you're using but to change the board logo on prosilver based styles...
Make your new logo file and save it as a gif, jpg or png file.
Upload it to your forum/styles/stylename/imagesets folder
Open
imageset/imageset.cfg
Find
Code: Select all
img_site_logo = site_logo.gif*52*139
and edit the logo name and dimensions accordingly.
Admin panel>styles>imagesets>refresh
Then hold shift and refresh your forum index.