I was just stumbling around on the internet and came across an excellent reharmonization of the tune Silent Night.
I do not personally know the guy who did this, but judging from the leadsheet and video, he has some excellent reharmonization chops.
You can compare this to my video lesson of my reharmonization of Silent Night. To be honest, I like some of his choices better, but I would keep many of mine too. I just might steal a few of these!
Seriously though, I can’t stress the importance enough about having a really good sense of jazz harmony and reharmonization when you sit down to write a chart. Practice and study it constantly. Becoming highly skilled in this area will help your charts sound much better.
Video of him playing through the tune. Follow along as he plays through it.