The Sprite Mastery Pod, an exclusive Chapter 7 Season 3 Battle Pass Back Bling, lets players display their favorite Sprites inside a protective glass container attached to their character. To unlock a Sprite for display, you must first reach Mastery Level 5 with it, although not every Sprite is eligible.
In total, 79 Sprites can be showcased in the Sprite Mastery Pod. Players who want to keep displaying them after the season ends should make sure to level them up before the opportunity is gone.

The supported Sprites include:
Some Sprites remain unavailable for the Sprite Mastery Pod even after reaching Mastery Level 5. This is most likely because they are tied to crossover collaborations, creating licensing restrictions.
The unsupported Sprites are:

As a Reminder, How to Complete Your Fortnite Sprite Collection Faster.