When it comes to flowers a great place to start getting ides is theknot.com. If you know your color palette I would suggest searching by color to get ideas, however you can also search by arrangement or by bloom.
After looking around on theknot.com I suggest going to fiftyflowers.com and searching your choice even more. Here you can select the color you want and look at all the different types of flowers in that color. I followed these steps and ended up with a few ideas for flower arrangements for the wedding in my film. Here are some of the arrangements I like, hopefully you will be able to get ideas for your color palette as well.