Hey everyone, here is a quick tip/tutorial on how to get those missing images when scraping with RetroPie built-in scraper (Yes, it can be done), and how to add your own scrape images instead if you choose to.
I discovered this method when I tried to scrape images from alternative scrapers but they didn't show up on the games lists forcing me to further inspect the built-in scraper.
Special thanks to RetroPie Guru's:
Easy Hax
Floob
ETA Prime