Here is the whole cast of Equestria dices I made so far (mane6 and "alternative mane6") along with the dice cup with the stylyzed Princess Celestia and Princess Luna.I am considering making more such dices, but it is not always easy to come up with sensible groups of six for a dice.
The CMCs along with Babs Seed, Diamont Tiara and Silverspoon might be an option, or the pets of the mane six (though there it would have to be a depiction of them rather than cutie marks). When it comes to royalty the four Princess + Shining Armor and either Princess Blueblood (who doesn't really deserve a place alongside the others) or Flurry Heart (who doesn't yet have a cutie mark to pick) come to mind. Symbols for villains or former villains could make a dice with Sombra, Crysalis, Discord, Lord Tirek, Nightmare Moon and Starlight Glimmer (but in spite of the danger she created the later seems very out of place there).I'm also thinking about dices with places rather than Characters (e.g. Canterlot, Ponyville, Cloudsdale, Manehatten, Crystal Empire and Appleloosa or the like).

Anyway, do you have any ideas or suggestions for interesting six combinations of characters or places (or other stuff) for MLP themed dices?