For wedding flowers, choose what works the best for your tastes. For example, you can choose wedding flowers that are all the same flower. Or, go the opposite route and choose a variety of different flowers. You can keep the look the same by repeating the same thing or being completely different.
For wedding flowers, you can decorate your wedding with one type of flowers and then decorate the wedding reception with a completely different look. Or, try to keep them the same or similar for more fluid look. There aren't any rules about the flowers that you use.