Marriage ceremonies can be as elaborate, large, and long as desired, at its core getting married is a simple arrangement requiring the individuals being married, a single witness, and a document. There are very few requirements for this document, and as a practical matter it can be inscribed on anything handy- though as a general matter some care and pride are taken with regards to this document.
Kilts are standard garb for bridegrooms; a kilt is considered a sign of virility.
During the Great War civilian marriages were different from military marriages, and there were various more casual affairs as well, however there were more requirements for a marriage, including requiring three witnesses rather than one.
While not many men have more than one wife in most places there is no law against polygamy, nor even any strong custom. Few men have two wives, and even fewer have three. The only customary restriction imposed is that a man must have enough money to keep two (or more) families, and a home big enough for them.