you certainly can keep your images in image folder. To do that, you would need to download your image folders from your live SBI! site and upload to your new host using FTP. Once you do that, you can just copy over images and paste into your WordPress without actually uploading it there.
The reason why I didn’t include this in the tutorial is:
1. Most people who use my WordPress tutorial usually don’t want to use FTP.
2. Image folders copied from SBI! site will not be a part of your WordPress site. They will display just fine, but technically they are separate. There is no problem with that as long as you remember about it at all times, especially when you move your site around.