If you want the games themselves to look as good as your new theme, try adding HD Texture Packs Custom Citra Themes | how to install on android
The subreddit r/Citra has a monthly “Theme Sharing” megathread. Look for posts by users with high karma. citra android themes link
After testing dozens of community threads, here are the safest places to get working (as of 2025): If you want the games themselves to look