Josenev, wow, those are coming along nicely.
Okay, let's see where things stand.
I think you're still slightly over budget on color count. As examples: In the case of the girl, I think you just have two slightly different whites, so they're trivially merged; For the boy, I found a stray reddish-brown (200/72/48) color that was barely used, and a very light pink that could probably be merged with white; The sprite has a hair color and skin color that could probably be merged.
The absolute limit for each character is 15 colors. The boy's darkest color is the color of all shadows in the game (heroes, monsters, bosses, townsfolk, treasure chests; everything), so it's ideal to make sure you like whatever his darkest color is as a shadow color. A second ideal would be to keep the girl to 14 colors to match vanilla (because her unused color can be repurposed), but that's not essential, more like a request.
You used a color to anti-alias the baked-in shadows, but there's a good chance that wouldn't look good in-game with the wide variety of ground colors and that's assuming the default oval shadows are disabled for the heroes (otherwise those pixels would be visible against the default oval shadow placed under the heroes).
For tiles, it looks like you have them all fit within the vanilla constraints, which is excellent. To be precise, your boy frame 3's upper tile would need to be shifted right another pixel, but that's minor (sorta, I know adjusting a tile's worth of art can be anything but minor).
The next limit to keep in mind is that you don't realistically have control over how many frames are in an animation. So the horizontal walk animation is just 4 unique frames in a 6 frame loop (1,2,3,4,3,2), like how you have it for the sprite. The upward walk animation is only two(!) unique frames, with each being horizontally mirrored to pad it out to a 6 frame loop. The downward walk animation is 4 unique frames, but two of the frames aren't near the others numerically (3, 4, 211, 212), probably because 211/212 were added later when they realized mirroring the asymmetrical boy looked bad.
Running animations also use some of the walking animation frames, so keep that in mind when you progress to the running animations.