Welcome to Pish Posh Peacock!
A year ago, I had my third child and I had to have a carseat cover! So I have a awesome friend who showed me the ropes, and I've been making them ever since!
Here are some of the features of how I make my Carseat Covers:
Gathered Back 
Wind, rain or shine. The top of the cover will not fly off!
Side Tie
Decorative stitching
I have different stitches, be sure to check out the Stitches tab for the one you want!
Double Layer flower ontop of handles for a Girl cover.
Rick Rack sewn over the two layers to add to the cover.
I like to be unique and have my Carseat Covers stand out. Instead of having both sides of the cover being the same fabric, I switch the fabrics up and have them both shown on both sides. This wasn't done on purpose, it was one of those BIG mistakes I made when I first was learning, but turned into a GREAT idea!