Actual lines are very obvious. The eye can easily follow the design to its height and width. Actual lines sets up the skeleton of the design. Actual line flowers can be curving and flowing within the design. Implied lines in floral design provide a pathway for the eye to follow but no actual line flowers are there. Although carnations are not line flowers per say, if they are cut one taller than the other that can create a line effect. Greenery can also create a line effect. As our eyes connect the upward graduating carnations we see a line result. The third kind of line is the psychic line. This is a line that does not exist, yet we feel the line outcome. Psychic designs are made by placing flowers in a manner that directs the eye up and throughout. Two tall birds of paradise can be placed high in an arrangement, while all other flora materials are rather short and to the base. The two tall birds of paradise create a visual line and bring the visual path upward. Many oriental designs use this technique.
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.