Hashim Warren's article introduces Challenge 3 of the #100DaysOfGatsby initiative, which focuses on teaching participants how to optimize images on Gatsby sites to enhance site speed, a notable feature of Gatsby. The challenge encourages developers to incorporate images into markdown-based blog posts and utilize the gatsby-image feature to auto-optimize them. Participants are tasked with creating an "About" page using JSX and transforming a normal selfie into a square, black-and-white image using the gatsby-image API. The task aims to familiarize developers with the impact of images on site production and user experience, and they are encouraged to measure site performance before and after image optimization using tools like Lighthouse. The article also provides resources and community support links for those who might face difficulties, emphasizing the community-driven learning experience of the challenge.