Johan Arwidmark is basically a guru in the world of Windows deployment. His blog (deploymentresearch.com) is a literal treasure trove of information for all things deployment related and it is where I found this tip.

By editing your CustomSettings.ini file you can actually set the resolution values to be written to your unattend.xml file during deployment. How handy is that!?!

Set the resolution to 1280×1024

[Settings]
Priority=Default

[Default]
BitsPerPel=32
VRefresh=60
XResolution=1280
YResolution=1024

Even cooler is the fact that you can actually set it to auto detect the resolution.

[Settings]
Priority=Default

[Default]
BitsPerPel=32
VRefresh=60
XResolution=1
YResolution=1

The auto detection works because Windows realizes how silly it would be to have a screen resolution that was only 1×1. Now that’s a neat trick!