Night at the casbah conjures up - least in my mind - roses and candles in votive cups and gypsophilia and rose petals leading up to the entrance. Perhaps use some lace or lace ribbon woven through.
Now for the convex curve let me think.
How about taking a large styrofoam ball and cut in half and then glue it to a flat surface like wood and make the arrangement on that half moon. Perhaps get one of those japanese fans and stick behind for more convex effect.
We need Terri on this!