Hello, not tested already for office 2013 but you can add an "OEM installation" to win8 DVD without problems ... At the end of win 8 installation the setupcompete.cmd launch the script to install your favorites programs in silent mode before opening the first session ... tested and worked here with 8 and office 2010 and many other programs in my script like Windows 2012 essentials , adobe reader, Firefox , Winrar , nero etc... My script detects also x86 or 64 install to install 32 bits or 64 bits version of programs like office ....
Or you can use Audit mode and reverse integrate Office 2013 into your next Win8 image. But this a very time consuming process.