These can be earned during Groups and Fandom anniversaries through Stage Quest in the Music Arcade. They can also be obtained during Idol Birthday Events. They are also purchasable through bundles in the shop during an anniversary of an Idol, a Group or a Fandom.
You can use these to purchase anniversary themed Concept Photos (profile picture) or Profile Skins. You can check out the catalog by going to Collection Book → Artist → Select an artist of your choice → Concept Photos/Profile Skins.
The first row is usually the Anniversary or “Birthday” theme as seen below:
An Anniversary Concept Photo requires 4 Anniversary Collection Tickets to be purchased
An Anniversary Profile Skin requires 10 Anniversary Collection Tickets to be Purchased
<aside> 💡 Not all Anniversary Concept Photos/Profile Skins will be available to purchase and will be made available on an irregular basis over time.
</aside>
These Concept Photos give Card Stat Buffs and other Bonuses which you can read in detail here: