I doubt that you showing or not showing the slide will make much of a difference one way or the other, but as a general rule, if I were one of the professors at your defense, I would not expect or want you to say or display anything that makes it seem like you are trying to ingratiate yourself with me in any way other than by performing well and conducting yourself professionally. I don't need to be thanked profusely, and don't need to be "appreciated" in any special way for doing my job.
Moreover, if you think about it, the reason something like National Teacher Appreciation Day was conceived is probably because in many countries being a schoolteacher is a very ungrateful, poorly appreciated job. For example in the U.S., teachers get paid very little, are commensurately not respected by much of society, and sometimes are outright hated by certain people for purely political reasons. All of this does not apply to university professors, who are generally treated quite well and held in pretty high regard by most people, and consequently aren't in great need for a "professor appreciation day".