The World is often a positive card for marriage because it represents the accomplishment of a significant desire.
The Hierophant is representative of all the customs and traditions that marriage brings with it. This is one of the most robust indicator tarot cards for marriage for this exact reason.
The Three of Cups doesn’t necessarily point to marriage directly, but this tarot card does represent celebrations like baptisms, weddings, engagements, births, etc.
The Justice card, along with the Hierophant, is one of the most powerful marriage indicators. A combination of these two points directly to a legal marriage.
The Lovers is a very obvious candidate for tarot cards that indicate marriage. Adam and Eve, the first couple in the World- literally represent this card.