There are lots of great elements to incorporate from the movie. I love the vintage-inspired wardrobe, the downtown Los Angeles location, and Tom's love of architecture.
sources: Our Labor of Love, Leo Patrone, 500 Days of Summer movie, Chuck Zlotnick/Fox Searchlight Pictures, 500 Days of Summer movie, Jordan Gray Creative via Oh So Beautiful Paper, Martha Stewart, Design Sponge, 500 Days of Summer movie
I picture a rooftop wedding downtown with lots of little white lights. Pops of blue color - including a vintage blue dress for the bride. Hope Hanafin, the costume designer for the film, choose to use the color blue as an accent and I love that idea. Hope said it was the romance from a male point of view. Even when you first see Summer, she has on a white shirt, but still has a blue butterfly. So it tracks all the way through. I just wanted there to be a way to make her stand out. She becomes a magnet. The only other place blue is used is the dance sequence, after Tom's first night with Summer. The whole world would turn into her, so that’s what everyone is in blue in that scene — the construction workers, the mailmen, the office workers. Everything becomes kind of a reflection of his love for her. What a perfect metaphor for a bride. :)
Another element that I think would be fun to incorporate is the use of a chalkboard (Tom had a chalkboard wall in his apartment). And the night would end with some karaoke - maybe even a Hall & Oates dance number :). You make my dreams come true...