If you're looking for art, I can recommend SukiiK's work as an artist, btw.
A few constructive things, now that I have a little more time. I'll focus on a few things, but don't take that in the way that the rest doesn't matter:
Game is difficult, but doable. Spot on. Try and keep it at this level.
Personal favourite is the succubus stage, the drone-bats create a very effective boss effect. The motions work the best in that one too, in my opinion. Love the kegelcising! The 'I'll swallow you whole!' at the beginning works very well too, is that from a Castlevania?
Naga stage is very well done as well, especially the game over by the first-part small nagae. Makes me think of that older game; Milia Wars, I think. This one's better though
Second part is good too, with the false hope with the exit. The insertion by the boss Medusa is well done as well, kudos. Internal stage is a nice transition as well. Third part opens strong, but then the stage is empty for the rest. Are you planning on putting something there? Jumping back in is a great option, but animation-less for the most part; Shantae just vanishes when she touches the boss.
The boss is also completely frozen at this point, maybe there's something to do with her changing stance when Shantae's near?
For both of these, when the stamina bar runs out and Shantae's trapped, you can struggle in four directions, each producing a different sound. This works very well, but you could expand on that a little, as it gets a little repetetive. Maybe add a fifth, orgasmic, sound clip that plays every 5 or 6 struggles?
Gourmet stage boss kinda freaks me out, but that's personal taste. Stage is fun, good use of the X from Metroid Fusion! The animation that goes with a failure is good as well! Something you could do is turn the sprite gradually monocoloured (the same colour of her skin would probably work best) between her kneeling and the 'poof'?
Pokemon stage is creatively done, the riding in a Goodra is a good find, never thought of that!
That's about all I can think of at the moment. Whatever you do further with the game, the best of luck with it!
Love, CapturePoint.