Twitter originated as a purely text-based social media platform, but as of the last several years they have allowed images to show up by default. No more clicking to see an image that is attached to a tweet. This makes the experience more immersive, and more immediately relatable.
Shortly after this new feature was added, BufferSocial did some research on how images effected tweets. Using a sample of 100 tweets they concluded that the use of images increased shareability in clicks, favorites and retweets. So if you are looking for a way to be a bit more influential, think about adding an image to your next tweet.