1) Gnome control center "details" section: Add Purism logo
2) Replace "9-dot" Gnome "show applications" with Purism rectangle
3) Consider using background logo extension https://extensions.gnome.org/extension/889/background-logo/
https://int.puri.sm/product/specs/pureos/configuration#changing-the-default-gnome-9-dot-show-application-button-to-something-purism-brandable-including-purism-branding
Also see https://tracker.pureos.net/T112