A customer has requested a yellow cake with a blueberry cream filling. I questioned her about what kind of cream filling, but she has no idea. I'm thinking about doing a blueberry and cream cheese or a blueberry and pastry cream filling. Since I'm from Maine, I will use fresh blueberries since they will be in season at the time of her wedding.
Any other suggestions?

Here is one from ladycakes:

http://ladycakes.com/Recipes/Fillings/blueberry.htm

I have been making a simple filling that can be used with different fruits. It originated from a pumpkin fluff filling I found on ladycakes also.
The basic ingredients are Cool Whip and vanilla pudding mix. Just blend those two together and then sitr in your favorite fruit. So far I've tried it with pineapple and bananas (separately). After blending in the fruit the flavors meld together. It's really quite nice. The pumpkin fluff filling also requires cinnamon.
Good luck!