In Yu-Gi-Oh, when you banish cards from the field, can you banish spell and trap cards in addition to monster cards?
There are three types of cards: Monster, Spell, and Trap. If one of these types are not specified, then it is assumed to be any of those types of cards. In this specific case, that means that Eater of Millions can indeed banish any type of card.

If you were only allowed to banish certain card types, it would be like Bazoo the Soul-Eater, which says that you banish "monsters" instead of "cards":


  Once per turn: You can banish up to 3 monsters from your Graveyard; this card gains 300 ATK for each, until the end of your opponent's turn.


This card would not be permitted to banish spell or trap cards.