What are the spacers called the can be used on a stacked caked so it can have flowers inbetween the tiers? Are they made from styrofoam and are the flowers just pushed into them? Where can I buy those online?
There are two approaches to flowers between tiers. One is styrofoam and you can order cake dummies and use them as spacers. You want them slightly smaller in diameter than the tier that will go above them but not so much smaller that they are unstable. The height of cake dummies is generally 4 inches which is a lot of space to fill. You could cut them down if you wanted but they are expensive. You could make your own out of purchased styrofoam. In both cases, cover the styro in something food safe. I used the same fondant I used on the cake so they didn't show. Some people cover with ribbon and the bottoms with something like press and seal. If you are talking real flowes you can use flower picks to push them into they styro. If you're using gumpaste and they are on wires or toothpics you can push them in. If your gumpaste flowers are not on wires you can attach them to the separators using melted chocolate.
You can also you a plate and pillar system like SPS (my preference) or Wilton that use taller legs to leave space between the tiers. Here is a pic of the Wilton ones. http://www.wilton.com/cakes/tiered-cakes/push-in-tiered-cake-construction.cfm
You can then fill in the open space with flowers. If they're fresh flowers remember that they should not come in contact directly with the cake and if they're gumpaste you may want to make groupings before you place them into the open space so you can adjust and fill in gaps.
Hope that helps.
Thank you so much! You're response is extremely helpful!