There is nothing that says they have to be the same creature
The only thing the spell says about what creatures are summoned is:
You summon fey spirits that take the form of beasts and appear in unoccupied spaces that you can see within range. Choose one of the following options for what appears:
- One beast of challenge rating 2 or lower
- Two beasts of challenge rating 1 or lower
- Four beasts of challenge rating 1/2 or lower
- Eight beasts of challenge rating 1/4 or lower
Nowhere does it say the creatures have to be the same or put any other restrictions on the identities of the summoned creatures. Thus, they can be different. If there was a restriction, the spell would say it.
It is worth noting that, per the published Sage Advice compendium, the intent is for the DM to decide what creatures are summoned.
Work with your DM if you want some input on what creatures are summoned.