In the past you wereable to set margins and borders when you insert images to the content.
Since WordPress 3.9, these options were gone.
If you miss them or if you want to have more control when you insert an Image:
You can install the "Advanced Image Styles" plugin to bring these options back.

This where my first 10 Wordpress plugin tips of 2016.

I hope you enjoyed it and will test some of them...

Grtz,
Bert