I was trying to figure out when I first came up with Light Rising and scrolling through my photos to do so. That's when I found my old Hrann designs from March 2021. 
Here's her current design! Most changes were due to backstory changes and simplification for a webcomic. 
It took me from 2013 to 2020 to come up with Dot's final design (mostly from a fear of getting started...) so... I have lots!
First design of Dot. She was 16-18 at the time, and thus had boobies and a butt.
First appearance of the forehead curl.
First appearance of the chest plate shape and the hair bow. This was followed by a ridiculous number of variations of her suit (I think I must have come up with close to a dozen).
Getting closer to a final design here, with the colors and some elements of the suit. She is also now 12, because I decided I want a precocious child rather than a teen. From here I abandoned the idea for 3-4 years I think? But I kept occasionally noodling with the gloves/gauntlets because I couldn't get them right.
When I eventually made up my mind to start the comic, I finished the design, simplifying it significantly for ease of drawing:
Interestingly-enough, I came up with Halcyon Days, her space ship (and the second MC), on basically the first try. I tried out other shapes after this one, but eventually returned to the very first design, whose only inspiration was "not another phallic space ship design" lol.
Very first design:
Evan Moriarty
He started as a supporting character in original version. The story changed over a decade from demons, to zombies and finally to a fictional infection. Evan modified to suit the new story and is now the MC along with his brother Owen.
Ver 0: The hero in original had to babysit a delinquent young man who evolved into Evan.
Prototype Hero: He evolved into a more of a serious character 
He evolved into a cold and deadly assassin but soon abandoned it (had started experimenting with a new art style)
The final (current) story Evan became the carrier of a virus that turns anyone he makes contact with into feral monsters. Powers come via symptoms developed by carriers (including Evan) based on States of matter. Evan having the ability to Solidify his body fluids, his saliva being the most convenient in combat. His personality became mischievous while remaining heroic, guess taking bits of his old versions.
Final 2d Concept & 3d version used in comic
Prototype Infected were basically Zombies
Final Infected are no longer zombies & are entities that fluctuate between states of matter, immune to gunshot, can teleport & spill through porous surfaces.
Now that's a cool thread! 
While I don't like spending too much time on character design, I usually do have a beta version. Most times it's really rough sketches to find out what I like and what doesn't click.
For example, Hexameron characters changed quite a lot, because it was a big cast. But the ideas behind the characters were simple, so it wasn't much work. 
GoA had a unique vibe, so I struggled with clothes a bit. 
Some characters like Hadis here didn't click from the first shot. I probably spent most time on her (including my writer's ideas about her) and the full design still isn't completely finished, to be honest. Her face and attitude shined on the group sketches, so I am happy with that. 
TiaT designs were really quick, I wasn't in the mood, so I went and started comic barely having completed characters in my mind. So the first episode featured Vulf in a "I have no idea how you're wearing it" cape and Beleard with a nose. I got rid of it the next episode 
I'm working on the main cast right now. I was going to do manga style, but that's WAAY too much detail.
Edit: And then I go ahead and add too much detail anyways. FRICK.
I don't have any images on my computer but I do have at least 20 prototype designs of my comics mc bc he took forever to get right ;-; I redesign my characters until I'm completely happy with them bc often I have a very specific image in my mind of what I want. The length in my process is often a matter of execution.
Here are Elsie prototypes
Here is Elsie 
Spring Heeled Jane
Roy
Anton Curtis and there was going to be a surgeon who did surgeries out in the street. That’s what they did. I felt that it would be too graphic.
And here is Ernest. He was going to be in his 30s or 40s in the early drafts.
When I announced I was making a new series (Frostpeak West), I posted this image of the characters.
Most of the boys look the same.
The girls however changed a lot.
The pink hair girl sort of evolved into the mean girl who yells at Ken in the lunchroom.
I thought Zanna (yellow girl) looked too much like Mabel from Gravity Falls so here is another prototype of fixing that.
Tilly (green girl), I just wanted to make her more curvy. (2nd image is how she looks in the final comic).
Tamara ended up as a mix of both the pink and purple girl.
For the teachers...their prototypes just look funny
You can see Sung and Robin's updated designs on this page.
TBH, I didn't really feel like drawing Robin's dreads even tho I think this design is cute.
Burnetto (blue guy) was originally dressed in an outfit inspired by old navel uniforms. I ended up just changing him to look like a stereotypical sea captain instead.
Then there is this alternate design for Zeta which I ended up not using.
When I first decided to start drawing again after a 25 year hiatus I bought a Surface Pro 8, a stylus, googled "good free art programs", downloaded Krita, and drew some characters.
And I hated them. I decided to spend some more time on them and made them look much better.
I do. Astra's armor and the shape of her face was different from her final design. Her scepter was different to. This is her beta design:
Her final look:
My early version of Maor looks very similar to current design.
->
For Amin I have a early sketch
He wasn't fat, just a stocky guy.
current character ref :
Early design of Sanariya vs character reference one (some colors on her clothing isn't accurate)
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She continues to evolve a bit more, her recent appearances in the comic has a bit more slicker face feature. Still I can't quite keep her looks consistent like my cat boy Maor.
2014:This was the 1st time I drew Akina(top left), Niyu(top right), and Jakira(bottom right) for my now defunct series Love Me Deity
2015: 1st redesign. I swapped Akina and Niyu's ears since I felt her uptight skittish attitude was more cat related and Niyu's carefree personality was dog like. Jakira had the most drastic change(2nd from right). My series took place in a country where the majority were dark skinned, but most of my main characters were light so I wanted to reflect that better. 
2019: When I finally released the series they went through a wardrobe change and I toned down some of the loud colors
In my upcoming reboot everyone has natural colored hair & eyes and pointed ears(cat or dog). I also curled Akina's hair since I thought it was cute
I found a run cycle animation I did for the original design of Dagnu (2015):
Prototype Dagnu and Sirona:
Final Dagnu Design:
Lighter red color with yellow markings inside of the legs, yellow on arms were removed, light brown hair added.
I actually draw her and her prototype as a chibi side-by-side
Which is which, do you think? I still have fondness towards either design (despite their flaws and stark difference in approach)
Najm and Alya were pretty solid from the start - the general forms of the Tazdahir uniform (tracksuit with turtleneck) was made pretty out of the gate. Qam and Rahat were later additions and were much more fluid - Rahat got a whole different hairstyle and vibe, neither of them had very solid personalities - the whole plot of STS was very wibbly wobbily in the beginning. It's still a little wibbly around the edges.
current designs.
Thank you! Its so cool to see everyone's characters and growth as artists!