Thanks for your comments SCD and Granville!
About the suggestions:
1- You might consider adding back in the red colors on Yoshi and Mario. Yoshi's spines, saddle and shoes. Along with Mario's hat. Donkey and Diddy still had their red clothing highlighted during these levels, in spite of everything else being blacked out.
Actually doable, for some reason I had the feel I've tried to do this before, but I haven't lol.
It actually works fine (though baby mario's mouth when he is on bubble looks a bit odd
but not a big deal)
2- You might consider swapping the palette of the waterfalls to an orange hue instead of the blue. Reflecting the colors of the sunset.
This is somewhat hard to do (but doable) because the animations of the game are hardcoded, so for modifying them it's needed to apply more complex ASM codes that unfortunately I don't know at the moment
(technically I only used STA's and LDA's for make this palette)
3- This is an extreme suggestion that some may not like, only if you REALLY want to clone the DKCR silhouette aesthetic. You could reduce the colors on the rocks and plants in the background layer. Most of the background objects in DKCR's sunset levels have all detail removed and are only a single color. Except for the sky and the water backgrounds. It's kind of reminiscent of Another World's visuals. If you do decide to do this, don't reduce the amount of colors on the sky or waterfalls. They look great with the extra colors.
This is very doable too (except for the waterfall colors as I've said before) however I don't think that would go very well, at least not with some YI backgrounds that already are somewhat minimalistic, but I'll give a try, after all I'm plaining to edit the palettes more (the background is technically using a unedited palette from the original game)
Thanks again for your comments I really appreciate them. By the way, here is the same effect with another backgrounds combination:
(It'd be cool to have the sun and the waterfalls together but that's not possible