It's kind of like getting an attachment to your tricycle to make it a bike. There's no reason to go back but maybe you'll decide you like alpha transparency more than ease of use and solid feel.

That simile totally broke down halfway through.

Evrey color has ist own RGB triple, except now instead of 256 (0-255) possibilities for R, G, and B, each now has 16 (0-15). However, color pickers don't support color scales with a maximum of 15 so we need to map that onto the 255 scale. This can be done by multiplying (I use trick's scale because it has a maximum of 255 instead of 240) each of the values in the 0-15 scale by 17 (11 in hex). For example, we have arbitrary color (0,4,6) in the 15 scale as (0,68,102) in 255-scale RGB. In hexadecimal that 255-scale color is (00,44,66). This 16x16x16 color space gives a full palette of 4096 (16^3) colors from which you pick your 32, as opposed to the 16,777,216 (256^3) colors in the 255 scale. So our 15-scale RGB color space has the same range as the 255-scale one (min=0; max=255 after conversion because 17*15=255) but less precision of color picking because of its smaller size.

To simplify, each color's R, G, and B values should be multiples of 17.

One thing I'd like to ask is: What kind of trees had bare stretches of trunk between large leafy areas? I've never seen any like that and from an evolutionary standpoint it doesn't make too much sense. I guess it's possible though, if not logical; are you basing them off of a particular type of tree?

This is a nitpick and should be regarded as such.

See those eye/bulb things? Grossness would approach maximum if you made those bulge out some and then return to normalcy.

Aside from that I can't really say much--your pixel skills are great as usual and your animation skills are even better. Except, maybe, the purple that's one shade beneath the green might be a bit too dark.

I would think of style as more of a reprioritization or selective emphasis than error. For example, some styles prioritize readability over anatomical accuracy because of small size, and others might prioritize realism or smoothness over low color counts.