There are two types of attributes for wing decorations and base skins: decoration attributes and activation attributes. You can view these by accessing the decorations from the Iron Blood relic building or Command Center and clicking on the desired decoration to see its properties.

For decoration attributes, you will gain these attributes only when the decoration is activated on your base.

As for activation attributes, once you’ve used a decoration from your inventory, the attributes will be activated and directly added to your base's total attributes. It doesn't matter if the decoration is currently active on your base or not. If you’ve used the decoration earlier and it’s still active (i.e., not expired), then your current base attributes already include the activation attributes of that decoration.

Note that each activation attribute is counted only once, even if you use more than one of the same decoration item from your backpack. These attributes won’t stack for the same decoration.

The more activated decorations you have, the more attributes you'll gain, as each decoration you use from your backpack will grant its specific activation attributes.