Consider the patterned papers. The "b-sides" are some of my favorite! Many of the die-cuts and stickers also work well for non-birthday pages, especially the wordless tabs, labels, tags, and arrows. And the colors of this kit are drool-worthy to say the least.
Here's my layout loosely based on an awesome sketch that Susan Stringfellow created for Scraptastic's 4th Anniversary Celebration:
The white die-cut phrase was a leftover from a previous kit and the enamel dots were from my stash, but everything else can be found in the Celebration main kit or its add-on.
I pulled out all my leftover enamel dots and used the smallest to embellish the wood veneer gumball machine:
Funny how the "Let Them Eat Cake" sticker works with my page about PANcakes!
I'll surely create at least one more birthday page (we do have seven birthdays in this very house each year!), but my plan is to use much of the paper for other happy colorful pages and save the extra themed stickers from the kit for cards, as I'm always looking for birthday card sentiments!