I won’t take the credit for this. I saw someone mentioning it. @themattelliott to be specific.
The gist of it is that there is a little website which will take instagram photos (yours, someone else’s, from a tag, etc…) and generate a background image for you which you can stick onto twitter.
This is what the website looked like when i was building mine.
The tool i used is called “instabg” and you can find it on instabg.com