When we begin the story, character creation will initially be limited to handful of races and classes/archetypes. If a race or class/archetype isn't on this list, it means that based on the original conceptualization I have for how the story begins I don't think those options will be available or functional - it doesn't mean a flat NO, but we'll definitely need to talk about things not on the list.
Human (standard human, no variant), Halfling (both PHB subtypes, Ghostwise, Lotusden), Dwarf (both PHB subtypes)
Barbarian (Berserker, Ancestral Guardian)
Bard (Lore, Valor)
Cleric (look at the religions for available gods)
Druid (Land, Moon, Shepherd)
Fighter (Champion, Battle Master, Rune Knight)
Paladin (Ancients, Vengeance)
Ranger (Hunter, Gloom Stalker, Monster Slayer, Beastmaster)
Rogue (Thief, Inquisitive, Scout)
Sorcerer (Wild, Divine Soul, Shadow Magic, Storm Sorcery)
Warlock (Chain or Tome, any patron in PHB)
As a huge fan of some of the some of the older D&D stories like the Dragonlance novels, I'm not wholly against the idea of evil characters; however, even Raistlin had a driving reason to continue with the Heroes of the Lance. If people are thinking of playing to some of these tropes, I wouldn't IMMEDIATELY say no, but I would also recommend watching Matt Colville's discussion on non-heroic and evil characters; I would also recommend discussing these ideas with the other players before you commit yourself to such an idea.
Because I am planning to use Milestone XP, I would like people to have some ideas about who they are as individuals and what is important to their characters. I will be awarding group milestones towards advancements as plot-lines advance, but I would also like to award individual milestones to people who accomplish personal story goals.