i dusted off my old designs of storm but im not exactly sure how im going to put it into the game, im no coder. prob just make a concept art of what i think she should look like and go from there. got alot on my plate atm but ill attempt to post something soon.
I usually just mod things for myself to tweak things I don't like personally in games but given the effort that goes into making a mod for this game from a coding perspective (its beyond my limited skills) I can try help with this one. My approach (again self taught so there are probably a million better) to redoing storm would be unren the game then overdraw her various png's at their relative positions/scaling & then keep the filenames so that everything aligns properly (layer them up to check) and you then you dont need to tweak much (if anything) in renpy. If you only want to do 1 body then just save it under both names. Looking at this mod seems they have put all the same named files etc. in a folder and called it 'modified' or something, placed within the character. Although to be honest a straight up replacement would be easier and better as its not just a new skin tone or hair style, rather a total replacement so any futher modifications would come off that.
Also I did notice that the storm 'sprite body background' png from the games files is actually diffrent hips and legs to the standard sprite when overlayed , looks better proportioned (more like the hourglass look from evolution storm) & the 'tits up' png actually works standaline (i.e. doesnt look werid not being help up by an arm etc.). If you made those the standard, moved feet over to the background sprite & tweaked the clothing I think it would be an easier option than scratch.
If you do have any art and want a hand put it up and I can see if I am able to modify existing clothes etc to fit to cut down on any workload- my art skills are at a level where 'from scratch' character art is extremely difficult for me but I can generally copy a style/colours/shading to modify existing things or make simple addittions such as the clothing etc.
Pretty sure that as the game got more popular the dev started adding more things to peoples varied interests, so some would love the muscle astetic and play with mostly storm, others prefer the frost lady etc.