I’ve found an outstanding collection of images and discussion on Portuguese tiles by historian Celso Mangucci: portuguesetiles.home.blog.
As you may detect from a sample of images here, Portuguese tiles are amazing. My wife and I visited Portugal a few years ago and I’ve always wanted to write an article on the topic.
Celso Mangucci has already done such a good job, the best I can do is point you to his site.
I am trying to connect directly with Celso to learn more about him and his research activities. In the meantime, enjoy the outstanding work he has compiled on the topic at his blog site!