I was in the process of looking for a tutorial for myself so i thought I would post what I found.
Here is a link to a picture of a wedding cake w/Poinsettias that I did this past weekend.
There is also a couple of close ups in my gallery.
I really enjoyed making the poinsettia. I used gumpaste that I ordered from Global Sugar Art. It is by Marcela Sanchez and is wonderful to work with. I was able to roll it out very thin. It takes a bit longer to dry than Wilton's gumpaste but is much better quality.
Justbeck101, thanks for the links and Karen your Poinsettia Wedding Cake is beautiful!