This is a brief guide to hopefully point you in the right direction.
Download CinematicUnityExplorer
UnityExplorer is a helpful Unity mod which gives you access to Freecam so you can take pics of whatever you want in whatever angle you want.
I personally use the Bepinex modloader to load the mod into the game.
Under the misc. tab, there should be an option to take a screenshot. There is a scale multiplier, I recommend 2-4. The screenshot will be saved in your game folder > bepinex > plugins > cinematicunityexplorer > screenshots.
Taking HD screenshots is a little clunky. In my experience, the built-in screenshot taker doesn't work, but Brian seems to have put in his own high res screenshot taker. You'll have to add the script "TakeHighResScreenshot" to whatever object, it doesn't particularly matter. Whenever you click, it will take a high res screenshot in the game's save folder.
(Generally this will be "%UserProfile%\AppData\LocalLow\AckkStudios\YIIK_ A Postmodern RPG")
If you wanna mess with the size it takes pictures in, disable the script (so you dont take 500 pics on accident and keep lagging the game) and click on it and you can find a size parameter to mess with. Then re-enable it and try again.