Google doesn't require an update to your app for you to change your screenshots so you can do it at any time in your Google Developer Console. Here are the steps to change them:
1. Go to your Google Play Developer Console
. Here's a direct link: https://play.google.com/console/u/0/developers
2. Click on the app that you want to change.
3. Click on Main Store Listing
. It's on the left menu under the Grow section.
4. Go to the Phone screenshots section
. It's under the Graphics section.
5. Upload your images. You can either drag and drop or click the Upload button.
6. Click Save
. Bottom right corner of the screen.
It usually takes 1 day for the changes to take effect.
We can help you by phone or email.