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:
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.
Hi LDiego_Intel, after digging around the build directories and harassing one of the yocto guys, the answer is to add to conf/local.conf :
IMAGE_INSTALL_append = " connman-client"