how would you do this cake? the bride wants cream cheese icing and a square cake but this design....

There are some crusting cream cheese frosting recipes on this site.

You could do this all in frosting except for the flowers. Ice the whole thing, then do the green. Pipe a small border where the green should stop. Fill in from there to the bottom, and smooth it out. Pipe the scroll border with a larger tip, and the squiggles with a small round tip (say a 2 or 3).

You could use silk or fresh flowers if you don't do sugarpaste.

You'll be fine!