There are some really cute cat rubber stamps at craft stores or online. If you are looking to make favors, you could stamp a cat (or pawprints) onto little paper bags, tie them with raffia, and fill them with some sort of treat (maybe swedish fish... or some kind of candy that would tie into the cat theme). Then your daugher could use the same stamps to decorate her wedding album or make her own thank you notes.
Joanne's Fabrics has cat themed fabric, which you could use to make table runners or mats to go under your center pieces. Your centerpieces could be stuffed toy cats with a vase of whatever flowers you wish. Stuffed toy cats can be found in thrift shops, or perhaps your daughter has a collection.
Stores like Dollar Tree usually have ceramic cats of various sizes that could be used on the tables also. You could also ask on your local Freecycle for cat items.
Have you seen the remake of "That Darned Cat"? They had lots of women wearing little cat ears on headbands, and I thought they were incredibly feminine.