While I think the art assets themselves are good, the biggest issue I can see with your UI is the inconsistent spacing. The two most obvious cases where this is visible are the dialog select brackets and the inventory screen icon positioning.
Notice how it looks like the corners of the brackets don't line up with the corners of the box formed by the text? This can be fixed relatively easily by making them align with a diagonal line shooting in the corner's direction.
The way stuff is laid out in your inventory screen is also a bit misaligned. The time in the top right corner is placed a certain distance from the edges, while the icons in the top left are almost right next to the border of the window. The player is also in a bit of an akward spot, almost overlapping with other UI elements. Finally, while the map is in the middle of the blank space to the left of your inventory, the looking glass on the right is right on the edge. This is all minor stuff to fix though, and a quick mockup shows how you can change the positioning to make it look a bit better. It's a quick and dirty edit though, so there could be more changes that would make it look even nicer. You should definitely keep messing with all this to find the layout that works best for your game.
So yeah, tl;dr is that you should make sure things are always aligned properly. That's honestly half of UI design. Make sure things are aligned and spaced out in ways that look good and convey what goes together and what doesn't. Other than that, you've got a good start. I look forward to seeing your progress on this!