A glance tells us we're waiting to hear from:

[M] Spiderman
[M] Wolverine
[M] Joker
[M] Ra's al Ghul
[M] Loki
[M] Venom
[M] Doctor Doom

which is a long list. Since most were active Day 0, I expect we'll see them long before Day 1 is over. Not to be a raincloud, Galactus, but when is Day 1 over? I didn't see a time limit for it.

Two people I don't think we've had the pleasure of meeting and greeting are Joker and Ra's al Ghul. Please do not lay low, if all the other trees grow tall and strong, what sunlight will help you blossom into the wonderful players you are?