The mansion design looks great, but I think you should work on the landscaping and plants:
- The hedge around the house should be more natural, and have some height variation and extend out a little in some places. Look at the bushes in front of the house in the attachment.
- The grass stripes can work, but they need to be a block that isn't so bright, something that matches the grass better.
- Don't use default trees, they're too boring and plain. Try making your own trees, look up some tutorials on YouTube, or find some trees from a tree pack. Good trees make your build look a lot better.
- A one-block fence doesn't look good on a house that size, make a fence that is two blocks tall or more. A nice simple design you can use is a stone-type block with a different slab on top.
Also, I don't like the big wall down the middle of the house, it sticks out too much. You should try to make it smaller or do something so that it doesn't take so much attention away from the rest of your mansion. But, make sure to work on that yard. A build looks a lot better when it's surrounded by great landscaping.