Customise the KTOOLS Photo Store gallery software.

We have created a site based on the KTOOLS Photo Store template. I need someone to customise the template to be able to upload and preview 3d cad files with the file extension .stl. So when people upload one of these files, the image library shows a still shot of their upload in the gallery. Currently, if you upload it, it shows a blank thumbnail as Photo Store does not have previewing ability for that file type. Our website is hosted on a shared server, so we do not have the ability to put other software on the server, so any solution would need to bear this in mind. WHEN REPLYING, PLEASE SHOW YOUR UNDERSTANDING OF THE PROJECT BY REPEATING HOW YOU WOULD TACKLE IT. ANY AUTOMATIC REPLIES WILL BE REJECTED.