I attempted to do a tropical arrangement the other day. It was a bit tricky because the stems of most tropicals are pretty tough and weigh alot. It is hard to get the stems to stay in the right places. I used a whole lot of shells and less flowers than I had originally planned and it worked. The good news with tropical arrangements is that they last for so long.
I added some raffia and a folded tea leaf at top of arrangement for more visual effect.