No horizontal mirror - the sideboard is enough of that. Find a lovely big mirror for over the sideboard - perhaps a white chinoiserie style one.

Scones will go nicely with tea, when you serve it.

As for sconces, you could get ones that hold candles.

How much of the sideboard do you want to finish? Do you want to keep the blue?

Could I do floor lamps on either side in lieu of buffet lamps? I have never seen anyone do that and I can't find pics on houzz so I'm thinking it's a no-no? I have a candelabra so no need of candle sconces. I meant to write vertical! A vertical mirror. I love my blue sideboard and in real life it works for me.

It's my mom's candelabra and it's staying..so I'm not sure if I could do buffet lamps?

What does a white chinoiserie mirror look like?

I have no problem with floor lamps beside the buffet. It is what I have done although my style is more contemporary/modern. I prefer the buffet decor to be less symmetrical.

No horizontal Mirror. Your room could use the height

Nothing you have in the dining room is modern

I'm not sure why you brought up 'modern'? It's obviously not modern! lol