The account owner can customise the certificates presented to users by uploading a new background image. 

The background image can be uploaded by selecting “Organisation > Settings” from the top menu.

To add your own graphics to the background of the A4 landscape certificate you will need to use an image 3508px wide by 2480px high. The picture below and attached template indicate where system text will be added to the certificate.

Certificates are created on-demand when users download them, this means the user will see the new design when they next download a certificate, regardless of when they completed their course.

Tip: Ideally your background will include some kind of faint watermark in these areas to help prevent users doctoring certificates, while keeping genuine text easy to read.

A PSD document with these areas indicated is attached to this article which you can use to aid the design of your templates.