Suspended cards are face up and can be examined by any player, as can all cards that are removed from the game, unless a card specifies otherwise.
The rules actually are very specific. It's just that there are so many of them that it's hard to know where to look. Here are the relevant rules:
217.7b Cards in the removed-from-the-game zone are kept face up and may be examined by any player at any time. Cards “removed from the game face down” can’t be examined by any player except when instructions allow it.
502.59a Suspend is a keyword that represents three abilities. The first is a static ability that functions while the card with suspend is in a player’s hand. The second and third are triggered abilities that function in the removed-from-the-game zone. “Suspend N—[cost]” means “If you could play this card from your hand, you may pay [cost] and remove it from the game with N time counters on it. This action doesn’t use the stack,” and “At the beginning of your upkeep, if this card is suspended, remove a time counter from it,” and “When the last time counter is removed from this card, if it’s removed from the game, play it without paying its mana cost if able. If you can’t, it remains removed from the game. If you play a creature spell this way, it gains haste until you lose control of the spell or the permanent it becomes.”