Where to Host Your Blogger Template Images
When you add images to your posts, by uploading them with the image tool in Blogger's post editor, they get hosted in Google's Picasa web albums. If you go to your Picasa web album account, you can upload images but there is no option to get a direct URL for any image you have uploaded, you just can send share links which leads to a page showing the image. But you can get a direct URL by uploading your template images from inside Blogger's post editor, using the image upload button in the compose view, choosing the "show original size" option and copying the image URL from the Edit HTML view.
Once you have the image URL you can delete the post draft, knowing that the image will stay hosted in your Picasa account, ready to be hotlinked from anywhere in your blog template.