Yes you can , but this feature is available only for 'Onboarding' and 'Training' plans or if you have 5 or more LTD codes
For adding your own certificate template, follow these steps;
Login to your academy dashboard
Navigate to 'Settings'
Click on 'Certificates'
Add new certificate or edit a certificate
Click on 'Upload own template'
Save :)
Let us know if you are facing any issue.