Custom Branding is applied to all existing computers via the auto-update process.
Once your Custom Branding is approved, the new image & wording is typically visible on your end-users' computers within two days.
Due to system caching, there are cases where an old logo can be displayed even after updating. Restarting the client computer or re-adding the PreferencePane will often resolve this.
Learn more about Custom Branding on this page.