Actually, that is a very good question, Andrea. I had the same one a while ago.
The problem I saw myself confronted with, was that I wanted to change my pictures on my website regularly, without having to change, build and deploy the website repeatedly.
We need to be aware that creating a responsive website is not the same as creating a dynamic website. When working with Site Designer, we are always dealing with predefined, static content.
Therefore, SD is currently not the tool to tackle these kinds of problems easily.
But while I like working with SD, I've decided to program a solution to the problem myself.
Please, take a look at the result at
www.sikkes.de/ . (Okay, the site is not perfect yet, but I’m getting closer…) All the images you see are dynamically loaded into the page. For this I had to write PHP, JS and CSS. The only thing I have to do now to change the content is to upload new images to my webspace or delete old images.
Henny is right when he says SD is a designer tool, not a site management tool. If we want more than a static site, SD combined with the chosen framework will only give us a head start.