I really couldn't care how wide the banner is but if anyone makes the width of the content fixed then I'll fight! I like that it's flexible to work with every monitor and device I use and not cluttered like other boards that shall go unnamed
JuzMel's banner quoted in this thread breaks the display on an iPhone do might be a smidge too wide in regular place.
But Griffin has plans for the banners so don't get too far ahead of him. If anything creative people like Juzmel and Skywarp should look at ideas for the "home page". That's my thought anyway.