Hi Mr.John,
I believe some users are currently working on modifications to the current images, perhaps you will have some ideas from the current discussion and tutorials, I will recommend you to verify the following information:
Building an linux image and modify the kernel - Answered
Build debian Linux distribution for Galileo board with debootstrap ,
How to enable the Yocto-provided package management capability
Galileo WiFi configuration http://www.malinov.com/Home/sergey-s-blog/intelgalileo-addingwifi ,
Building Linux Image http://www.malinov.com/Home/sergey-s-blog/intelgalileo-buildinglinuximage
I will search more information, in the meantime I hope these documents can work as a reference for your project.
Regards,