Currently, we only have a spring and winter major event, "Spring Loaded" and "Winter Event". I do have some ideas for summer and fall events:
For the summer event, you could have Lara embarking on a tropical adventure and battling tropical enemies of sorts, such as creatures or guardians of aquatic legends and myths. An associated outfit for this event could be a new one - the wetsuit from Tomb Raider II. It could have a new ability that grants her a temporary attack speed boost every time she dodges an attack.
The fall event could be Halloween-focused, like Fortnite: Save the World. Lara could battle undead and terrifying creatures and face rewards for overcoming fears and conquering the darkest tombs. An associated outfit for this event could be the doppelganger outfit, since it carries a spooky demeanor.