Unfortunately, the gallery always starts with the first image.
I'm not sure what you would rather have. Please explain in greater details what it is that you are trying to do and I'll try to help you out.
If you are looking to have your thumbnail links go to different images within a gallery, then set enableDirectLinks="TRUE" (in JuiceboxBuilder-Pro's 'Customize -> General' section) and you can refer to specific images with a # identifier at the end of the URL. For example http://www.example.com/gallery/index.html#7 would go directly to the 7th image in the gallery.
Would you be able to tell me what is the correct spelling for the linkURL...
linkURLs can be set on the 'Images' tab of JuiceboxBuilder.
If an image has been assigned a linkURL, then this URL will be opened when the user clicks the Open Image button (when showOpenButton="TRUE") or when the user clicks the main image (when imageClickMode="OPEN_URL").
linkURLs can be relative (to the page containing the gallery's embedding code) or absolute in the form http://www.example.com/index.html.
linkURLs are stored in the gallery's 'config.xml' file.
A sample <image> entry containing a linkURL will look something like this:
<image imageURL="images/IMG_0001.jpg"
thumbURL="thumbs/IMG_0001.jpg"
linkURL="http://www.example.com/index.html"
linkTarget="_blank">
<title>Image title goes here.</title>
<caption>Image caption goes here.</caption>
</image>