Both Facebook and Twitter allow you to upload your own custom headers... are you making the most of that space?
Check out the examples in the article, and also consider who are your colleague authors - those whose books your readers love, too - and go to their pages on social media to see what they're doing with that space.
Be aspirational - check out what the best-sellers in your category are doing.
Be strategic - Diana's roundup gives some handy design categories these fall into, including:
Promote a single book
Promote a series
Display multiple books
Showcase art from a book or cover
Focus on author branding
Be creative - use a free tool like canva.com, or a more robust designer tool, or consider hiring an actual designer to help make you look like the professional you are.
Have fun with it, and know you can change it up over time!
Illustrate and Write On,