The number of people who are allowed to certify content should be pretty limited, and should only include people who are knowledgeable about both the data and the certification requirements. Ideally, certification should only be done by domain/subject matter experts — and this isn’t usually your Power BI administrator. In larger organizations, you might reference multiple Azure AD security groups in the tenant setting – but it should remain a pretty limited number of people to ensure that the certification designation is truly meaningful. (Note that we currently cannot specify who can endorse content on a per-workspace level.)
Read on for more information about content certification, as well as content promotion, in Power BI.