CSS Image Replacement

I'm trying to include images in a Masonry item. Adding images to a Masonry item works fine when the images are added to a node as image content. But when you try to add images via CSS Image Replacement techniques (assigning a background-image to a class), the images are not displaying on the Masonry item.

I've successfully displayed an image this way on the full node. When I look at the HTML being generated, I see this:

<img class="cs-tag-credit">

And the image displayed via CSS Image Replacement displays correctly, using the following CSS:

.cs-tag-credit
{
    width: 180px;
    height: 25px;
    background-image: url(../images/SubIcon-Credit.png); 
    background-repeat: no-repeat;
}

However, when I look at the HTML being generated for the Masonry item, I see this:

<img class="cs-tag-credit" src="">

So it looks like the Masonry module is adding an empty src="" attribute to the img tag, which is killing any image replacement attempt.

I tried looking at this in a non-Masonry view and the image is displaying fine. Views produces the same that is in the HTML I added to the node.