I am still not 100% sure what you mean about the background thing ... When Facebook shares an image, it will locate the image NAKED in your document page source. This is achieved through tags in the source code, for example:
<meta property="og:image" content="http://ia.media-imdb.com/rock.jpg"/>
The above is from Facebook's own documentation. Facebook find the page, located the image and or thumbnail, and shares it on some "wall" on facebook.com. It will not add any background or any other style, unless you background (or frame etc.) is in fact embedded in to the image itself. That is how it works ...
As for sharing urls, let me try to rephrase. Imagevue is a single document with a SWF application running inside. When browsing around the gallery, you might see something in the URL field like:
gallery/#/content/folder/
gallery/#/content/folder/image.jpg
gallery/#/content/textpage/
However, the anchors behind the # are not separate "webpages". They simply act as a mechanism for deep-linking inside the Imagevue gallery. When facebook goes to those two links above, it will see the link
without everything after the # sign no matter what:
gallery/
gallery/
gallery/
The stuff that comes after # is irrelevant for Facebook, and it sees the same URL, and correctly so because there is only one. The stuff that follows the #, is simply anchors and does not change what is inside the document itself. If you check the raw source in the document (for example in your browser, view -> source), you will see the same content no matter what. They are simply not separate pages technically speaking. They are a single document, and Facebook will read it as a single document. Only humans will see the links differently because the stuff that comes after #, actually tell Imagevue what folder or image to navigate to ...
This is why we have some special method for the sharing buttons, which I will not explain in depth. It involves forwarding a different URL with a landing page for a specific image, for Facebook to read and pickup the data for the specific image/folder. Thereafter, there is a javascript that redirects the human user to the correct location in the gallery ...