If you don't transmit values and touch people's heart, your preparation and work would seem boring and useless to them. Your conclusion must also deliver the sense that your speech is over, not just by saying "Thanks so much for your attention".
If you deliver the right value, your audience will thank you. So I want to propose you three excerpts taken from the following speeches. They have been greatly useful to me.
"Every problem you face is an opportunity for a creative solution. We each hold the key key to our innovation engine and have creativity waiting to be unleashed. It is up to you to turn the key."
—Tina Seelig video
"Our creativity comes from without, not from within. We are not self-made. We are dependent on one another; and admitting this to ourselves, isn't an embrace of mediocrity and derivativeness, it's a liberation from our misconceptions, and it's an incentive to not expect so much from ourselves and to simply begin."
—Kirby Ferguson video
"There is a mismatch between what science knows and what business does. And here is what science knows. One. Those motivators we think are natural part of the business do work, but only in a surprisingly narrow band of circumstances. Two. Those if-then rewards destroy creativity. Three. The secret to high performance isn't rewards and punishments but that unseen intrinsic drive. The drive to do things for their own sake. The drive to do things cause they matter. And here's the best part. We already know this. The science confirms what we know in our hearts. So if we repair this mismatch between what science knows and what business does, if we bring our motivation, notions of motivations into the 21st century, if we get past this lazy, dangerous idealogy of carrots and sticks, we can strengthen our businesses, and maybe, maybe, maybe, we can change the world."
—Dan Pink video