Regardless of the platform you use, be it Blogger, Wordpress, Evolution etc, switching to a new template is trivial. But, unlike for instance Wordpress where the images come in its own folder with the template, Blogger images are usually stored in free picture hosts. Pictures hosted at such places can cause you trouble in future:
- Uploader's account can be deleted for any reason.
- Such hosts often impose bandwidth restrictions and you can suddenly see warning messages in your blog, or no images at all.
- Template writer can accidentally delete those images.