If the logo (banner) is designed for the largest screen resolution it shouldn't lose proportion when the media queries cause the site to be responsive on smaller screens.
There is no setting that will allow you to modify the resolution of the logo image.
Without more information, the only thing I can guess is that your logo is either too low resolution, not transparent, or surrounded by too much "white space."
If you want to post (or PM) a link I can possibly get a better understanding of the issue and help you resolve it.
|