A party theme can be inspired by anything - a color scheme, a decade, a food, a Disney character, an ugly Christmas sweater, a country, you name it - a party has been planned around it.
While the purpose and person of honor should be at the forefront when deciding a theme, you should also take into account the time of year, party location, and guest list - their ages, dietary restrictions, and the sheer number of invitees.
Now to narrow it down.
To License or Not:
An easy way to weed out theme options, especially for kid's parties, is to decide if you want to select a popular character and use the licensed party supplies that go with it. For example - If you went with a Dora the Explorer theme, you could then just buy the Dora licensed plates, napkins, party favors, wrapping paper, balloons, invites, thank you cards, etc etc etc. While it might look like Dora threw up all over your party, a die hard Dora fan would probably love it, and while you would lose originality point from the pinterest crowd and it might cost a little more, it would save a lot of time and energy.
Select the person of honor's favorite character and use them for inspiration. Maybe splurge on a few Dora themed party supplies, but draw the color scheme from the show - Pink, Orange and Purple? - Transform plain purple gift bags into backpacks full of treasures. Put a Swiper No Swiping! sign above the birthday gifts. Set up a multipart treasure hunt for the main activity. Decorate with stars and send invites that look like rolled up maps. Use your imagination or scour pinterest and google image searches for ideas to swipe.
Is it Limiting?
I tend to start my party planning by selecting a color scheme or design. Hannah's 1st birthday was inspired by a multicolored polka dot dress I found at Nordstrom Rack, and our Christmas party was a mixture of blues and silver with lots of shimmer and snowflakes for a winter wonderland feel instead of the traditional green, red, and Santa. Polka dots and snowflakes are easy to decorate a party with. Banners, serving ware, invites, and wrapping paper can all be incorperated easily into those themes. But for Hannah's 2nd birthday party I considered doing chevron themed decor in a certain color scheme:
I just couldn't seem to make it work easily. I couldn't find scrapbook paper with a nice chevron, so I couldn't do a banner or bunting. And while I COULD find lots of digital scrapbook paper for download, I didn't want to rack up a huge bill at the print shop. I could find chevron gift bags, but giftbags weren't a huge part of the party - although I did make them for the kids. I couldn't find serving platters or even paper plates with chevrons on them, and I couldn't find a premade dress or even fabric in a chevron design to make an outfit for H. Hense, it just wasn't working.
While a color scheme or pattern might look great in your mind, if you can't find the supplies to make it work, then you should probably rework your concept. Unless you want to stay up all night piecing together strips of paper to create a chevron banner. I admit, I considered it. But sleep sounded better.
For more inspiration, check out these great websites:
A huge list of party themes - birthdays and beyond - plus lots of real party recaps with pictures.
Unique ideas, beautiful pictures, and daily updates.
Hostess with the Mostess. Really, doesn't the title say it all?