Cucumber cactus: cucumbers, pickles, pineapple, and toothpicks to look like Radiator Springs decor.
Pig corraling - this would be great for a petting zoo/animal themed party
A handy collection of Western/Circus type fonts
Easy to make table decoration...Mason Jar Burlap & Bandana Decor / Cowboy/Cowgirl party @Jess Liu Sallee
Cut and paste cowgirl or cowboy from Making Learning Fun.
Cowboy boot craft - the link no longer works but you could just cut out a boot from brown construction paper and then glue on sequins and other fun crafts bits.
Cowboy Gross Motor Activity - Pre-K Pages
Cowboy Theme Bull roping. Love this bull! It will go great with Bessie the cow, two chairs and a yard stick! More
Paper Crafts for Children » Simple Cowboy Hat
The Entertaining House: 20 Winning Ideas for you Derby Party Decor