Presents for a professor can really give people an opportunity to be creative. Naturally, a professor's wedding isn't necessarily going to be all that different from most other weddings, and getting a present/gift for a professor won't feel like a college assignment. However, there are still specific ways in which people can celebrate a professor's love in a way that is very specific to them and to their interests.
In some ways, it all depends on which subject the professor teaches. History professors, art and art history professors, and English professors automatically offer people a lot of different options when it comes to present/gift ideas. Getting English professors first edition copies of some of the books that they teach, or at least autographed or otherwise famous copies of some of their favorite titles is a tremendously thoughtful wedding gift. Philosophy professors might be able to benefit from similar gifts, especially since many of the philosophical treatises that they teach are going to come in similarly historically significant editions.
Art history professors, and most other humanities professors, are usually going to have venerable offices in the older buildings on campus. It becomes that much more important for them to make sure their offices look nice. Getting an art history professor a beautiful print or reproduction of a famous or favored painting will usually go over well. History or archaeology professors are always going to love any artifacts that they're given, even if they don't directly relate to their exact specialty.
Getting gifts for professors in the sciences might seem a little bit trickier for some people. Humanities professors are genuinely people who study aspects of human society and human culture. Gifts are basically cultural artifacts themselves, so a lot of the gift ideas present themselves. However, there are artifacts from the history of science that plenty of science professors will love. Some biology professors will have various biological specimens around their offices, like preserved animal skeletons. Astronomy professors will usually have decorative and professional posters of various star systems or star charts. A lot of the equipment that science professors need has to be special-ordered, but there are plenty of specimens or decorations that they wouldn't order for themselves and that they would love.
Naturally, all professors are going to enjoy practical gifts. More furniture for their offices, nicer desks that give them more room, fancier desk lamps, and nearly anything else that is going to make their office space more presentable will usually make any professor happy. Lots of professors share their offices with several other professors as colleges cut their budgets and cut their budgets, which can leave a lot of professors feeling under-appreciated. Getting nicer office furnishings can send a lot of professors back from their weddings feeling happier and more successful already. Naturally, a lot of professors still haven't been able to afford the famous tweed blazers that they're all supposed to wear, and many of them would love to go back to work as the best-dressed members of their faculty. Gifts that reflect the interest of the professor or the needs of the profession are always welcome.