Hello,
This would be the only code that would specify width on the logo. Other than that there aren't any width limitations outside of the body width. Your best bet would be to possibly remove the width below and combine your images into a single image.
Template.CSS - line 653
.s5_logo {
cursor: pointer;
margin: 0 auto 6px;
text-align: center;
width: 340px;
}