The simplest mantle display I know is also a no-fail go-to.
Most people already have either a large mirror or piece of art over their mantle.
Add a couple of classic candle sticks with white or cream tapers. I used crystal holders, but silver, gold or wood work just as well!
Arrange a bunch of tulips in low container, round or square works best. (Other flowers work also, but none are quite as graceful as tulips!) Here I used a turquoise teapot.
I also left a couple of mercury glass votive holders up to balance the lamp I have near the other end, but you really don't need anything else up there!
Light your candles, sit back and enjoy!