More visuals for reference

Start by removing the black cage thing from the light I can't tell if that is photshopped in there to see what a new light would look like but IMO keep what you have, I see no purpose for a mirror there unless you always exit from that entry and want to do a last minute check. Yes a table would be good , where is the coat closet? From what I see nothing can really go on the stair wall since there is no clearance with the doorways right there .

The mirror is beautiful, but is just a bit big for that corner. Yes, a shelf or small table. Consider relocating it. Do you use this door a lot?
BTW, Love the light!

You need a rectangular table under the mirror for ”support.” Not too big, not too small.

More importantly, its hung wrong and looks wonky. Do you see it has 4 sides with longer, slightly curved edges? Take it down and rehang so those sections are north, south, east west. Also it might be a few inches too high but you can address that after the table is in place.

Too bad you don’t have an outlet there because you could put a lamp on it. I have places like that in my home, not enough outlets. Beautiful crown molding.

Any ideas for what sort of table? Rectangular??

If anyone has pictures of sort of table they would do that would be incredibly helpful! Thank you so much!

Like this?

Without a doubt, you need a cage thing. Senoia 31'' Console Table
https://www.wayfair.com/furniture/pdp/zipcode-design-senoia-314-console-table-w004998120.html

.

I think something in a wood tone would look nice and warm. I would go with something open and airy yet still with a couple of drawers so it does not get lost in the space.

How high is your mirror, it may be too high up. You can also place a bench and umbrella holder

Mirrors should be hung where they either reflect something beautiful or fill a functional purpose. Not sure this fits the bill. If it is functional in that location agree with small console table beneath, with a few things on it.