The Bowser victory pose has some problems with proportions, mostly because it's a WIP anyways I assume.
His arms are much larger than his legs unlike the original (I personally think they should be even instead, the original looked like a kangaroo, heh). I realize that his head casts a shadow on his belly, but I feel it should be bright anyways to show depth. With the sprite being much smaller because of his hair, it's important to make his limbs stand out and be large so he fills the most space he can. His toe nails are also dark and don't stand out/contrast well with his bright skin tone, and are a bit small.
You also forgot his shadow. Everything is looking good besides that. I'm loving the Mario Bros there, you nailed it.
EDIT: Also, your Toad's body is a bit 'tube-like'. Toad's body rounds in before it reaches his head, but yours goes straight up into his head without a curve.
His arms are much larger than his legs unlike the original (I personally think they should be even instead, the original looked like a kangaroo, heh). I realize that his head casts a shadow on his belly, but I feel it should be bright anyways to show depth. With the sprite being much smaller because of his hair, it's important to make his limbs stand out and be large so he fills the most space he can. His toe nails are also dark and don't stand out/contrast well with his bright skin tone, and are a bit small.
You also forgot his shadow. Everything is looking good besides that. I'm loving the Mario Bros there, you nailed it.
EDIT: Also, your Toad's body is a bit 'tube-like'. Toad's body rounds in before it reaches his head, but yours goes straight up into his head without a curve.