The Windows 8.1 ISOs are not what they used to be, for example depending on when you download the Windows 8.1 Enterprise with Update from MSDN you get different content.
When downloading it today (Dec 21, 2014) the file included the November 2014 updates. Here is a plain deployment, with no extra updates installed.
Note: The Windows Server 2012 R2 ISO is also updated.
Please use this one for your build and capture processes, it will be faster.