Looking from the screenshots so far, here is my input.
- The new tilework is great. I personally believe that every third generation hack needs new graphics, as the potentials have been unlocked and fully realized!
- A new player sprite might be appreciated. No one likes playing the same character, even if it's a different region (or at least I don't!).
- As for the tiles looking similar to those in other hacks, you should probably add a little personal touch. Perhaps darken it a bit.
- Since you are working with a new region and new Pokemon, I'm thinking this to give your hack a little edge: exclusively Gen. 4 and 5 Pokemon. Some other hacks involve regions from the anime, or modified versions of the Kanto/Hoenn region. You have a nice chance to start with a whole new Pokemon set..
Of course, these are just personal suggestions.