I've seen some softer lighting ones used to pretty good effect. The mods should be able to be found on the forums over at Hongfire. If you got the game from there you probably already have their patch, which IIRC includes a couple.
Alternatively, you can use the Huggingface WebUI to use a stable diffusion model. Just feed the image into the model using the img2img UI, making sure that the image itself is given pretty high precedence so the AI doesn't just overwrite it. My profile image is an example of this method, although I used GPT for this one not the huggingface UI. GPT will flip out if you give it anything more racy than bootyshorts however so I don't recommend using Dall-E for much. Getting it set up can be a little complicated, though.
If you do go AI, make sure you specify a medium to avoid running into the same issue from the other side (most AIs have their own generic-shit quality to them). My personal favorites are colored pencil or marker, but they can do stuff like oil paints, watercolor, wood print, sepia film, all kinds of stuff. It'll help the images look unique which is the goal.
Finally, you could simply take the images into photoshop, paint.net, or GIMP and use the basic filters provided out of the box with those. That's what I did for the aborted project I was working on, and the results were... Well, it's not the best option, but it's dead simple and is still a step up compared to raw KK screenshots.
The goal is just to soften out the monotonous KK look, so basically any filter is going to improve things at least slightly. Really, you'll have to figure out what tone you want the game to have first, and then find a filter that fits that tone for you.