Get some dry branches in a base...the lamp is on the small side...I would pick a larger one... Good luck!

I suggest a bulkier lamp with a fuller base & shade. At the other end, keep your candle holders because they'd be pretty illuminated in the evening. In the center, you could place a couple neat coffee table books or a shallow basket. You wouldn't have to balance the height. However if you do like symmetry, try two identical lamps with a slender base and fuller shade. They could even be a little taller, too. I think the problem is your lamp appears too dainty for the side table & thick framed mirror. Best of luck!

An alternative table lamp will suit it better. See examples:

a more substantial lamp would be a great improvement. try a pretty platter in the middle.

I'd like to see tall, matching lamps on either side of your sideboard, or possibly one tall and chunky driftwood lamp (see attached samples), for starters.

I suggest a pop of red.

Given the natural elements and bulkiness of your pieces, I would continue with an organic, heavier feel in your accessories. Wooden bowls, large candles, a larger lamp, etc and you'll have a cohesive look/style that will really catch the eye.