Hi Joy,
Using those colors, I'm sure your granddaughter will love anything you make, but I understand that you want to make something very special.
Try this site on the internet http://www.quilterscache.com
This takes, developed by Marcia Hohn you to a great site filled with hundreds of block patterns that I am sure you will enjoy.
Scroll down the page to the question "Where do you want to go today?" Click on the arrow and choose "Quilting Blocks Galore" from the list of choices. Then explore all the different blocks Marcia has provided. Be prepared to spend a lot of time; she has lots of blocks to look at. She also tells you which ones are easy and which more difficult. I am sure you will find something you like at your skill level.
If this is not a surprise for her, get your granddaughter to look at the blocks with you and let her choose a pattern that she likes.
As I said, because you made it for her, she will love it no matter what you choose. Good luck and happy quilting.
Connie