How to extract icons/iconography from APKs

I just want to know if it's possible to break open an APK (say from Facebook, Twitter, Periscope, Instagram, YouTube) to get their unique iconography sets (for personal UX concept works and uses only, their copyrights is all on them). Whether it's a sprite, individual PNGs, SVG files, or even better font glyphs? Where could I find them? Most of the time they're on assets, but most of the other time they're not? Where could I find them and extract them? Thanks