Customizer → Assets → Graphic library tab.
The graphic library is your curated set of placeable graphics. Unlike brand logos, customers choose to place them (and can move them like any graphic). Each graphic can be priced, tagged, restricted to products or categories, and marked recolorable.
Deleting a graphic hides it from new sessions; existing quotes keep it.
Customers don't see the library in the storefront. Set a zone to Library only or make sure uploads and the library are both allowed. If the library panel is not visible at all, contact support — it is enabled progressively.