I believe that if the green rounded piece at the tip is supposed to be circular from a front view, it would look more horizontaly squashed from the current side view.

Some of the rivets on the fin have their lightened parts reversed, I am not sure if it fits the direction of the light.

Maybe the three lighter shades of the wood surface shouldn't be so warm? It is a deep underwater scene, and the water would suck up almost all the red component of the light down there, the wood would get a sickly olive or some other non-red hue. However, that is open to artistic choice I think

Also, someone will probably give you better advice than me regarding the wood grain/texture that might be improved, but regarding the shape of the planks, I think they could show the curvature of the oval body instead of being rectangular all the way. I think I liked the brightness values of the wood in the first pass before the texturing.

Glass, glass is hard, take a look on what eishiya and Pistachio helped me with on another thread, perhaps it will help you:
https://pixelation.org/index.php?topic=26545.msg198345#msg198345

Overall I like it, specially the palette, the parallax idea for the underwater background (it will be parallaxed right?) and the fact it is that it is already very readable and non ambiguous, leaning more on symbolism then realism as is proper for a game-y sideview piece.

Second version is obviously more readable because you added another shade. It is not too highlighted yet to me, quite the opposite but that kind of thing should be judged against the scene, and depending on the level of focus you want on him I guess.

If you want to show more volume like in the second piece without making him generally brighter, then I think some dramatic underlights would fit very well. Can't think of anything else, but I am sure others here will have different suggestions for him.

Ah, to keep him more Spidey I would change his tophat into a bowler hat, so his head keeps rounded and more easily indentifiable coupled with the spidey eyes. I didn't knew it was Spiderman until I read your description

The pyramidal blocks in the middle look a bit shallow, I think the illuminated faces should be as bright as the highlights on rims of the other tiles, if not brighter.

Also, you are using the same middle color on the internal diagonals like they where an opaque 3d mesh defining the tappered shape of the blocks, but they are edges of a solid and should be highlighted on north and west like the  rims of the rest of the tiles.

Edit: I can also suggest that you could drop at least one shade on the hopscotch brick pattern, the internal shading inside each brick is barely visible, and it feels a little pillow shaded no?

Left hand has pinky sprouting out in a weird way, as if the hand didn't realy had enough space for it in first place. I never get hands at this angle right as well.

What eishiya said, you need to make the tiles "puff-out", try to remove the corner rounding on the bottom of the tiles, and aggressively increase the rounding on the top of each tile, so their are more like pillows nailed to the ground on the bottom edges.

The bottom shading of each tile should probably be as rounded as the rounding on the top of the tiles, and the contrast should be lower to imply a less plastic/ceramic material.

Textile materials have a lot of subsurface scattering, like skin, that greatly reduces shading contrast.

Also, If the splotches are stains rather than folds and depressions, then are likely to be from organic stuff (blood, piss, healthcare daily life), so they might get some warmer colors, contrasting with the more pure grey of the actual shades which are not stains.