Hello again! First, I apologize in advance - this post has probably been at least coming for a year or two given how long I've been working with the program, so forgive me for listing so much all at once.
Bodies: I think I mentioned this elsewhere, but one thing I'd like to see is the ability to change a sprite's height or width individually instead of just scaling the entire thing up and down. If this could even extend to different portions of the body (legs, torso, etc.) down the road, that would be fantastic, but at the very least, being able to change sizes this way would be a huge help.
Facial Features: Options for extra facial features would also be nice! Some examples of what I mean are different eyebrow sizes and shapes, beauty marks, scars, and so on! Different types of pupils (though I could be here all day linking references) would be another great addition, along with perhaps a single fang we could toggle on and off.
Expressions: I think the different expression types we have now give you a lot of options, but having worked with Mannequin sprites on my visual novel for as long as I have now, there are definitely a few that I've found myself wanting enough to just make for myself. These include:
- More "comical" styled eyes, such as ones like the half-closed one we have already, but tilted to express anger or sadness. Other "comical" eye types we could use include various types of horizontal-line based ones for tired or mellow looking expressions, your standard >_< X_X and I_I eyes, and so on. Here are some examples.
- Speaking of the comical eyes, some mouths to go with them would be nice too! Some examples of possibilities include a playful cat mouth, a mouth that's got a little drool leaking from tiredness or hunger, this ever important face, a half pout, a full pout, all kinds of exaggerated expressions like this, blowing a raspberry, a playful teehee going one way, and one going the other :9.
- As far as more normal expressions, one I've basically had to make for all of my characters over again is a downward wink - where the eye that's being closed is closed downwards, basically, so you can use it for more exasperated and tired expressions. I've also mixed the Frantic eyes around with other ones to create different types of wounded expressions and so on, though others' need for this type of face might not really warrant that.
- Other blush types and facial effects would be cool as well
Head and Face Wear: More accessories for a character's face are fantastic ways to make them easier to recognize and more unique! Some of the ones I'd personally love to have access to include baseball caps, baseball caps turned around, visors, headbands around the forehead, foreheadbands but tied on the side, goggles, maybe even helmets!?, or helmets?!?!, hairbands with ribbons on them, caps of varying shapes, round beanies, pointed beanies, cat ear beanies, puffball beanies, straw hats, sun hats, this hat, tippable hats, and punching hats.
Hair Styles: Besides the one I suggested from my previous comment (here is another reference), there are a few other styles I've had a real hankering for using Mannequin. The side-ponytail and side-parted bangs being able to be reversed to appear in the opposite direction would be another nice feature. The current ponytail (the basic one) is fairly limited as well. It could be longer, bigger, wavy, thin, curly, and more, such as-- Raised/upwards curved bangs, thicker twintails, thing long twintails, low set drills, swirly drills, big drills, full drills, etc. Adding variations of hair with Hair Intakes to the existing hair styles would also be a fun alternative. Some of the bangs have something similar to this, but they're not emphasized quite enough.
Accessories: Balls, bows, clips with different shapes, watches, and rings. I've got a lot of sprites like these in particular, some of which you can see here! Different accessories for other parts of the body (backpacks on the back, purses and schoolbags over the shoulder, etc.) also would be fun.
Clothes: A track suit, jackets and/or coats, and a hoodie jacket, ideally with options for these to be opened and closed each. For the button up shirts, being able to have characters with only one side tucked in (so they can appear sloppy or rushed) would be a big help too. This is pretty easy to make manually, though.
And that is... all for now!
Apologies again for the huge dump of suggestions. Here's a gallery that includes all of the linked images.