You could create an arrangement for any size vase, the larger the vase, the more flowers and greens to use. For Christmas time, use red, white and maybe even green flowers (like green button mums). Also choose from a variety of greens and evergreens out there. Accent a red rose in a bud vase with some baby's breath and cedar. Deep red alstroemeria are especially beautiful. There are many other flowers that would be perfect to use for Christmas arrangements, the link below will take you to a complete list of flowers, foliage, and evergreens for Christmas floral design.
Creating floral designs that catch a viewers eyes is a skill which good flower designers have. Just like an artist who creates a piece of artwork that captures the viewers attention, the florist needs to be able to create a design that pulls a viewer into a floral design. When pullled into the design, the viewer experiences something that must be good about the designer. It will help them to think positively about the designer.