I looked through your code and it seems that the post is divided into seperated divs, which will help to do this trick.
I will try to explain this the best i can, but as i don't know how familiar you are with html it might not be so easy to understand.
I wasn't able to find the theme so you have to add this code yourself.
First of all connect to your host and browse to the wordpress theme folder. Find the folder for Jillij-flash and copy the index.php and style.css file to your own computer.
With a text editor open up the index.php file and look/search for <div id="post"> - This will be the start of the post. Next find the ending <div> for it (The div will include both a div with the id entry and postmeta). Just above the closing </div> add a new div like this <div id="postend"></div>
This will create an empty block between each post so now we need to add an image to it. I've created one you can use as a test and replace with your own when you make one. You can get it here:
Place this within the theme folder under images (or change the path below in the css)
Open up the style.css file and go to the buttom and add the follow
/* Add image splitter between posts */
background: url(images/damasksplitter_bg.gif) no-repeat;
That should do it :)