Years ago I recovered one of our boosters to make it more enticing for my son as he was growing into the new seat. I recovered it with the fabric theme he liked at the time- Disney's Car's.
Now it's being used by another son and the fabric has gotten a little worn and this son is more of a Toy Story fan than Cars so I took off the old fabric and sewed new Toy Story fabric on.
It's like a brand new car seat, and personalized to the child's own taste which gives them a sense of pride in their car seat.
Recovering a car seat is pretty easy. Here are the steps:
1. take the covers off of the car seat
2. wash (if necessary- which usually is for my kids!)
3. lay your new fabric over the middle section of the car seat covers and cut out the shape/style needed. (this can be kind of tricky and take time and patience being careful you don't cut the car seat cover)
4. sew (I do a zig zag stitch) around the edges of the fabric on to the car seat cover.
I don't worry too much about turning ends under or having it "exact" because it's something that will get used and worn by the kids a LOT and may need to be replaced down the road. Plus rarely do people closely inspect the seams on your car seat. :)
And I even had enough fabric left over to make my son some matching shorts!