I'm not convinced you have the room or the sun for a potted tree on the porch. I'd plant up the planters on either side of the door and call it quits. If the area behind the wall is all paved, you could add a few taller plants in pots behind the wall.

All in all, it looks good to me. If the photo were staged, the porch wouldn't be in shade. My guess would be with a few flowers in your planters and a photoshop to take out the shade in the porch, you might have a wow pic. So, don't confuse staged photos for real life.

I would trim the window to match the door and the other window. Fill the planters. A rug as wide as that area not just in front of the door.

maybe some type of structure like this on the left wall with just the pots not the vine.

I too was thinking something for the left wall and if you have an outlet for adding a water feature to the suggested latticework would be nice for the sound in the enclosed space.

Use 3 of the large pots that are by the front door and place one each in front of the three posts. Then around the door have a grouping of small colored pots on the ground and plant stands.

A large bench under the window next to the door with a colorful rug. Maybe even a runner to the front door.

On the table, a flower pot and cute decor like a dining room, that's your rotating display.

For potted trees, in the corners behind the low walls.

The door could be a brighter color. It is set back in the shadows.

Here is a rough sketch of my concept, colors TBD.

If that is a beam over the columns and not just trim, it looks like it could span the whole width of the porch without a center support. If so, I would remove the center column and the Y braces and beef up the outer columns to echo the low pillars flanking the walkway. Then widen the door and window trim, add lanterns on the pillars, create a focal point on the left wall (here a trellis similar to the window/door trim with a climbing rose; like the above fountain suggestion too), add flowers in the pots and at the base of the existing shrubs. Framing trees would be nice if space allows (there are narrow columnar varieties). Could the table take an umbrella (high enough not to hit people walking to the door)?