Hello Supergoomba112! Welcome to SMW Central! I see you're new to SMW hacking as well as to the website!
Your title screen is kinda empty. The level should be not as flat as that and you may want to add some more info, like maybe your name and the period of the hack's construction.
I don't like the overworld's palettes, they're a bit too bright/saturated. Good palettes are not made in 5 seconds, you should listen to my advices. Your palettes should be not this saturated and you can use similar colors to each other, but with different brightness for a great effect. You need to work until you're fully satisfied. There are also a few cutoffs, like the left side of the waterfall or the water surface on the coastline. And one perspective error: the hill with the ladder looks like an island behind the main one, you should add some revelant tiles to make the hill look not like an island.
As for the graphics, you should make them so nothing's cutoff, i.e. the tiles should match with each other. There's only one problem with the backgrounds on the title screen level and the level showcasing graphics you made. It would make more sense if the water became lighter and lighter going up to the side of the sky and had a dark outline between the water and the sky. It would make more sense.
Anyways, I see the hack has some potential and you'll improve with the time.
EDIT: Added the word I forgot about.
I have a Discord server as well!
Basically, I believe in peace and bashing two bricks together.