Yes, many moodle admins use a customized background/watermark image and print only the name of the student, the date and perhaps the code onto the certificate.
You should consider using a png-image as a background for lossless quality.
I have modified my certificate module in a way that it doesn't print the course name but a topic or a title instead. I had to add some extra fields for this. I also found a way to put wrappable text boxes in the certificate. Now my teachers can fill out an html-textfield with a list of contents or learning goals that is printed on a portrait certificate.
Custom certificate (plugin)
Title for certificate unique code
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