We had the Reds Vs. the Blues just like the movie, complete with Mr. and Mrs. Featherstone (the flamingos): 
The cupcakes were red and blue gnomes "hiding" in the grass: 
I took sugar cones and coated them with melted Candy Melts, then sunk them into the frosting "grass" on top of chocolate cupcakes. 
The Travelocity Roaming Gnome made an appearance (found him at Target along with the fantastic mushrooms which I painted) as well as the stuffed crocheted version I made years ago. He (the crocheted one) lives in the center console of my car and has been photographed all over CA, WY, NM, CO, NV, UT, OR and even went with my parents and aunt & uncle to Hawaii two years ago . . . I have a whole scrapbook devoted to his excursions! 
The treats on the Red side were strawberries, dark chocolate Hershey candies (3 shades of red), cupcakes with Strawberry Fields ice cream and Coke and red Hawaiian Punch. The treats on the Blue side were blueberries, York peppermint candies (blue & white), cupcakes with Birthday Bash ice cream (confetti ice cream with blue frosting ribbons throughout) and Pepsi and blue Hawaiian Punch.
We had our own version of "Nanette the Frog" -- my mom's vintage cookie jar. That thing is older than I am and has been repainted several times but I love it! My dad would happily let it live at my house permanently but Mom wanted it back.
He had to eat the frosting first:
After the presents . . . the kid made out like a BANDIT, I tell you . . . and the treats, we all went back outside to launch the Gnome Paratroopers!
The paratroopers were a huge hit! 
And finally, we ended the night with Gnome tattoos. Those little guys were the HARDEST thing to remove -- they said "temporary" but 5 days and that many showers later I finally had to take the nail polish remover to mine and he still didn't budge. 
Josiah said he loved his party and had a ton of fun with all his friends and family. I was glad to hear it, because I had a blast! Love that little guy!
I sewed the flag banners the day before the party using cloth fat quarters and bias tape. We held the party in the back room of our church (since most of the invitees attend there, we wanted a central location that was large enough for everyone . . . and the place was packed!) My mom made the blue and green puffs to hang from the ceiling and we tacked up the banners in different places. 
Valerie also has a deep love for argyle, so the invitations (oops, photo of those to come) were argyle paper diaper bags. And since it was a brunch party, we had fruit and juices and we made muffins and frosted them with cream cheese. The diamonds are blue and green fruit roll ups cut up and the stripes were just more cream cheese dyed with neon food coloring. 
I crocheted the squares in the colors and in brown for a background, then set to work on making the half-squares to fill in the edges. Funny thing . . . half-squares are really just triangles (yes, I sucked at geometry) but crocheting them isn't as easy as it sounds. I tore out quite a few attempts before I got one that looked right. Perserverance, right? Finally the whole thing was done and I did a simple border to finish it off: 