Final answer:
Bob Ross is the celebrity with a dedicated Twitch channel streaming old episodes of 'The Joy of Painting' 24/7, contributing to the Twitch cultural experience.
Step-by-step explanation:
The celebrity who is an important part of the Twitch cultural experience with a dedicated channel that streams old episodes of their TV show 24/7 is Bob Ross. Bob Ross, known for his gentle demeanor and the TV show 'The Joy of Painting', has become an iconic figure on Twitch. Twitch hosts a channel dedicated to streaming episodes of his show, offering a space for relaxation and nostalgia for the viewers.