Appropriate to thank examiners?
Yes. 

It's a lot of work to examine a thesis and (generally) this is unpaid work done in our own free-time. So a simple thank you will make your examiners feel appreciated. This will have the side benefit that your examiners will remember you in a positive light, which may be useful in the future when you are looking for a job, for a reference, for a place to visit to give a research talk, etc.

It never hurts to be polite.