I found an old post that linked to a series of video tutorials with examples for customizing WPF controls:
Tutorial + Example Code for Building Professional WPF Apps - NI Community
It's a dead link but I searched the text and found this page which has the example projects (which are nice):
Customizing Measurement Studio WPF Controls for a Unique User Interface - NI Community
This appears to be a support page for the videos but it doesn't link back to the videos. Does anyone know if these are available to watch anywhere? If so, I would greatly appreciate a working link.