well how are you positioning the image?
You should put it in a div and postion it:
to do this:
Putting up your main image.
Upload it at
http://www.imageshack.usand then put it into this
CODE
<div class="bg" style="position: absolute; left:0px; top:0px; width:000px; height:000px; overflow: hidden;">
<img src="IMAGEURLHERE">
</div>
Change the top and left to position where the image is.
And change the width and height to the same as the image.
I suggest making the top about 160-170px
So its right under the navigation bar more than likely.
Really Just mess with the numbers and such and you'll get the hang of it