I don't mean this as an offense but aiming to recreate Cave Story's style is setting a modest goal for yourself, to say the least. Don't get me wrong I like the work so far but Cave Story seems to have been elevated to some graphical pedestal where it's the greatest thing since cheez-wiz. The fact is if you want to build off of what Pixel did in Cave Story you're going to have to be able to look at it with a critical eye and identify where Pixel's failures were so you can overcome them.
Now, this is art, so those failures/successes are pretty subjective. I know that I personally felt like the areas in Cave Story felt very barren. I didn't feel like there was any kind of coherent game world. There are a bunch of winding tunnels, because the game needed winding tunnels. And there are doors here and there, because the game needed doors. But who dug out the tunnels? Who put the doors there? Looking at Cave Story you get very little sense of actual story through the artwork, ironically. It's all incredibly generic.
I guess my point is that Cave Story has been done already, so if you're set on doing this project you have an obligation to surpass it, put a twist on it, take it in a direction that Pixel never thought of; otherwise I don't understand why an artist of your skill is bothering with it.