Performance

I'd love to use blotcdn for all my images for its convenience, but I find it extremely slow and unstable to access in mainland China if internet proxy not used. Therefore, I have to host all my images on a domestic cloud server, and embed them one by one in separate markdown files. For each individual post/entry, it works fine. However, the Portfolio template I'm using, still generates thumbnails from the embedded images and host them on blotcdn for the homepage and archives. I checked the fitted-grid.html file and tried to modify the and but have no idea what property should I refer to. Is there a way to use the original images from my cloud server for all the pages (homepage, archives, etc.)?