Windows Image sizes continue to get bigger and bigger.  I recently recreated my WIMs that I use for testing and applied all important updates through March of 2015 before taking the capture (using MDT of course).  For Windows 7 (both 32-bit and 64-bit), I started with the latest available Windows 7 Enterprise with SP1 ISOs.  For Windows 8 (both 32-bit and 64-bit), I started with the latest available Windows 8.1 Enterprise with Update (released in December 2014).

Prior to the capture, I ran the Disk Cleanup utility to remove any unnecessary files and reduce the size of the final captures.  Below is the end result with a comparison of the original ISO sizes.