I had the same Issue John.
I added some code to my custom override stylesheet - templates/rt_graffito/css/rt_graffito-custom.css
I changed it to this as inline border:0 is obsolete in html5
Source:
www.w3.org/TR/html-markup/img.html
Apparently it is fine via a stylesheet
templates/rt_graffito/css/rt_graffito-custom.css
/* Logo */
.logoimg {max-height: 50px; margin: -23px 0 10px -20px;}
div.rt-image .logoimg img {max-width: 120%;border:0;border-style: none;}
@media only screen and (max-width: 480px) {
div.rt-image .logoimg img {max-width: 100%;}
}
/* End Logo */
Custom Html
<div class="rt-image rt-center">
<div class="logoimg">
<img src="images/my-logo.png" alt="My logo" />
</div>
</div>
My Logo image size is 312 px wide x 82 px and sits nice now.
The margins in my stylesheet were just to position it better.
Also don't know if my code is valid but it works here on all devices
Maybe someone with a bit more smartz can clarify but as I said it looks good here.