The wall the sideboard is on is 13.6' in length and the width of the room is 9.5'.

Hmm, then there's probably not enough room to put the sideboard on one of the shorter walls. But there does seem to be some space to the right of the sideboard?

I don't want to push you into one of those top to toe renovations that sometimes happen on Houzz if you don't want one, of course. :-)

I agree with Rina that having the art hung so close to the sideboard and mirror won't look right. It will crowd the wall. The size of the art looks okay, but it might be too much for one space.

Size of new art is good, can be even larger. Height of light is good. Sideboard and mirror and the little stand are too much stuff for that room. Can you move sideboard to foyer or hallway or put in another room?

Sina Sadeddin Architectural Design, If all other pieces of furniture but the table and chairs are removed, is the artwork size appropriate?

Yes. The art size works well.