If the blog contains pictures that were uploaded using post editor, do not ever delete the Blogger / Google account.This detail, in some cases, seems to be seen as a myth or superstition.
Some superstitions have basis in reality - and this is one such superstition. When you upload pictures using the post editor photo upload wizard, they are hosted in a Picasa account that's tied to the Blogger / Google account. You can transfer control of the blog itself, using Settings - Publishing. Unfortunately, this transfers only the blog.
The Picasa account, where the pictures are hosted, remains with the current Blogger / Google account. If you "clean house", and delete the unused Google account, your pictures go away.
Here, you may wish to review the connections between Blogger accounts, email addresses, and Google accounts, as well as the original procedure for transferring control of a blog.