I would get a mirror and call it a day.

Problem is that tile you did on the baseboard area already looks like tile itself with black lines separating each tile. If you put tile behind the mirror It will look very strange with that type of footboard. Basically it won’t be pleasing to the eye. You should’ve done a basic footboard if you wanted to put tile behind your mirror, so it won’t give it a distracting look. Now your options are limited and it looks like the only thing you can do is just a nice mirror. If you want to do tile you’ll have to change your foot boards so you don’t get those divided lines. That’s the first thing that popped out when I look at the picture. I hope you understand what I mean.

Totally makes sense. I didn’t do a footboard just because it’s just not as durable in the fir finish and over time would look beat up.
I get what you are saying it confirms my initial thoughts.
Much appreciated