Target has these outdoor pillows right now that would look nice on your porch furniture:
Here are a few other combinations I made to show you how great seemingly unrelated pillows can look together:
The same green is used in these three pillows, and the patterns look cohesive together.
I think zebra print makes everything better, and I love the mix of an animal print with the two busier designs. The black keeps everything looking like it was meant to be together.
Black and orange are the common colors here, but they don't look at all like Halloween. I love the mix of Ikat, the abstract florals and fun polka dots.
I like this muted pallette with the light teal in the peacock pillow. The mixture of textures (silk, cotton, burlap) takes the mixing even further.
This is a colorful mixture, but would look great on a taupe sofa. The beaded pillow brings together all the other colors.
So get rid of the standard matchy-matchy pillows that came with your sofa (or better yet, put pillow covers over them), or the shams that came with your sheet set, and gather a collection of throw pillows. They'll make your room look put-together!