I like the palette here, except for the white in the bg which is too bright and kinda detracts from the overall dark vibe of the other colors. Also you should probably edit the palettes of the bushes and the white temple type thing (I forgot what their called exactly) as they don't quite fit in with their original palettes. The colors of the water in the fg also need some fixing. I don't know if you want it to be brown or if that's some kind of limitation you ran into, but if you can't make it blue (or don't want to) at least adjust the white to fit the rest of the colors a bit better.
You also have a bunch of cutoffs in there and while some people don't really care about them there are just too many here.
What's weird about the ground exgfx is that you only edited the normal ledge and not the rest of the grass tiles, so most of it is still the original gfx15, not sure if this is just a wip though.
That said I raelly like the animation of the water in the bg.
The level design on the other hand seems pretty bland. You only have one enemy in what looks like about 5 screens, which is going to be rather boring to play through. Again, I'm not sure if this is on purpose to create a kind of lonely atmosphere, but if not then please add some more enemies, even if it's just the first level.
Good luck, I hope my feedback kinda helped and wasn't too harsh
btw do I know you from somewhere? EDIT: Ja, dass tu ich
Schön mal wieder von dir zu hören, ist schon ziemlich lang her.