Every gallery needs to have a separate configuration file (default name 'config.xml').
You can certainly set Config Options in the embedding code (please see here for details), but image data cannot be set in the embedding code and must be set in the configuration file.
Even if you use a Flickr account as a source of images and set the Flickr Options in the embedding code, the gallery still needs a separate configuration file (even if it is just a dummy file with only a <juiceboxgallery /> tag) to function correctly.

Please note that if a configUrl is not explicitly set in the embedding code, then Juicebox will look for a file named 'config.xml' in the same directory as the web page containing the embedding code.

I don't know what your goal is or if it will help you out but you could use a PHP script (or use some other server-side scripting language) to generate XML content on-the-fly when the gallery is displayed. Please take a look at this forum post (scroll down to the answer to Query #3) which has an example of how this could be achieved to display all images in a designated folder. (You could change the code to pull in image data from a database or whatever image source you choose to use.)