I read in that referenced thread that these images are a slideshow, does that mean you know the width and height of the right "floated" block?
IF so the following fiddle example may be an option, if not I don't think it's possible without keeping the images first in source.
IF so, it means inserting one empty div first in source, dimensioning it to match the images/slideshow area and floating it right for a "placeholder".. then add position relative to your main content area, and absolutely position the actual images/slideshow over the placeholder:
example fiddle : HERE
full code as per comments :
HTML:
<div id="wrapper">
<div id="header"><h1>Header</h1></div>
<div id="tabs">Tabs</div>
<div id="main">
<div id="ssholder"></div>
<div id="left">
<p> Lorem ipsum dolor sit amet, consectetur adipisicing elit,
sed do eiusmod tempor incididunt ut labore et dolore magna
aliqua. Ut enim ad minim veniam, quis nostrud exercitation
ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit in voluptate velit
esse cillum dolore eu fugiat nulla pariatur. Excepteur sint
occaecat cupidatat non proident, sunt in culpa qui officia
deserunt mollit anim id est laborum.
</p>
<p> add loads more content!</p>
</div>
<div id="sshow">
<img src="" alt="" width="200px" height="50px" />
<img src="" alt="" width="200px" height="50px" />
<img src="" alt="" width="200px" height="50px" />
<img src="" alt="" width="200px" height="50px" />
<img src="" alt="" width="200px" height="50px" />
<img src="" alt="" width="200px" height="50px" />
</div>
</div>
</div>
CSS:
#wrapper {
width: 600px;
border: 1px solid #000;
}
#main {
position: relative;
border: 1px solid red;
}
#ssholder {
float: right;
width: 200px;
height: 300px;
}
#sshow {
position: absolute;
width: 200px;
height: 300px;
top: 0;
right: 0;
background: #eee;
}
#sshow img {
display: block;
}
jQuery to detect heights if not explicitly set on #sshow
:
$(function() {
var sshowHeight = $('#sshow').height();
$('#ssholder').height(sshowHeight);
});