Watch your consistency between the different views of the character. For example, the trousers get wider and the boots get narrower in the back and front views. The lighting is also inconsistent.
I quite like the details! The city's starting to look like a city. Watch your road widths though - as I and yrizoud said earlier, the roads running vertically should be wider than the ones running horizontally, due to the low camera angle (simulated perspective distortion).
For the hologram trees, try something like this, perhaps?
This is just a two-frame animation, each frame showing alternate lines of the tree. The lines are at full opacity, but because it switches between the frames rapidly, it creates the illusion of transparency while also having that "scanline" look that people associate with holograms. It's also more interesting than just a static image. If the tree is too opaque or too high-contrast like this, you could lower the opacity on the entire sprite (in-engine ideally, so that you can fine-tune the opacity to the location).
If you want the holograms to be static, maybe make alternate scanlines brighter/darker instead of having them all be the same? Visible scanlines make everything look like a screen/hologram 8]
As an additional detail, maybe have some sort of base under the holographic trees, so that they don't just look like they're magically projected out of nowhere? It's not important, but it would add more believability to the setting.