if you instead want all images on the site to have the padding-left of 15px but for the header image not to. Just go into your template file and change the following
<img width="640" border="0" src="/~tekspec/vasarelli/images/stories/wine.jpg">
to
<img width="640" border="0" style="padding-left: 0px;" src="/~tekspec/vasarelli/images/stories/wine.jpg">
This works because the direct style is applied to the element last which overrides the default img class.