Instagram removed support for Twitter cards in 2012, meaning your Insta images no longer appear in your tweets, just a boring URL. Use this recipe as a workaround, leveraging Tumblr as an intermediary.
If
New photo post
This Trigger fires every time you create a new photo post on your public Tumblr blog.
Then
Post a tweet with image
This Action will post a new tweet to your Twitter account with a linked pic.twitter.com image. NOTE: Please adhere to Twitter’s Rules and Terms of Service.
Explore more great ways to automate Tumblr (legacy) and Twitter