There is no way to change the name of the 'images' folder from within the JuiceboxBuilder-Pro interface but there are a couple of things you could do.
(1) After creating the gallery, change the name of the 'images' folder manually and then change all instances of 'images' (to match the name you chose for your image folder) in the imageURL entries in the gallery's 'config.xml' file. (This can be done quickly and easily with a single global search and replace action in a text editor such as Notepad++.)
... or:
(2) Give your gallery folder a unique name, upload the complete gallery folder (not just the contents) to your web server and embed your gallery into your web page using the baseUrl method documented here. (The gallery's 'images' folder will remain inside the gallery folder and will not clash with your own 'images' folder.)
For example, if your gallery folder is named 'my_gallery_folder' and you upload it to the root directory of your web space, then you could use the following embedding code. The leading slashes in the paths denote your root directory so this code will work in any web page throughout your site without modification (although you can change the gallery dimensions and background color if you like).
<!--START JUICEBOX EMBED-->
<script src="/my_gallery_folder/jbcore/juicebox.js"></script>
<script>
new juicebox({
baseUrl: "/my_gallery_folder/",
containerId: "juicebox-container",
galleryWidth: "100%",
galleryHeight: "600",
backgroundColor: "#222222"
});
</script>
<div id="juicebox-container"></div>
<!--END JUICEBOX EMBED-->
I suggest uploading the gallery folder to your root directory for convenience but you can upload it to anywhere on your web server that you like as long as the two paths in the embedding code (the path to the 'juicebox.js' file and the baseUrl itself, pointing towards the gallery folder) are correct.