This is just my opinion, Tom, but I wouldn't capitalize "birthday" in this sentence. Grammatically speaking, it doesn't need commas (more on that in a second). From a greeting card industry standpoint, I don't think I've ever seen a period at the end of a title, even if it was a sentence.
 
Having said that, I'll be honest and tell you I find the sentence a bit awkwardly constructed. Might it be better to day something more like...
 
"We should have known he'd have a speech prepared for his birthday"
 
Corrie
http://www.corrieweb.nl

I'm going to go with Corrie's suggested sentence recast. It accomplishes two things: 1 less word than my original suggestion. Without changing the font size, you only have so much room. And it puts the word you want to emphasize at the end of the sentence, so you can do away with the capped "B" on birthday. A word at the beginning or end of a sentence is going to get more attention when card shoppers are quickly scanning the card fronts.
 
Pattiann

I'm glad you raised the punctuation topic, Tom.  I find myself using a lot of exclamation points and "..." because the partial sentences and titles look so naked.  I was never tempted to use exclamation points as a magazine editor, but now I seem to get carried away!!!!!!!! See, there it happened again.  Thanks to everyone for their information, too.  

Thanks all.  Good feedback.  
 
As a kid I remember one of the funniest lines that perhaps got me started on my humorous writing ways.  It was "Throw Grandpa down the stairs his glasses."  I think I was about 8, and it was in an English phonics workbook.  That indirect object in a prepositional phrase can be made to sound rather funny, and I think it has caused me to naturally write in a twisted sentence structure like I did in the example above.
 
I'm going to stop adding periods.  That's good to know.  I likely will still capitalize Birthday on a Birthday card, for emphasis, and I'll now think more about untwisting my twisted sentence structure.  Commas are something I will have to study more and perhaps post the rules along side my monitor, or is it, perhaps, post the rules along side my monitor (?)
 
The reviewers have never spanked me for misuse of caps, commas, structure, or periods; only spelling.  Perhaps they should.  What do you guys think?  It could get a bit debatable, for instance do you use caps for:
 
1.  Happy Birthday
2.  Happy birthday to you brother   <---  
3.  Have a Happy Birthday
4.  Wishing you a happy birthday, brother
 
Thanks again!
 

Tom, that`s funny, when I was younger I was sitting in an Amish restaurant with my grandparents, and one of the ladies said..."Out`ten The Lights" meaning of`course Dim the lights, I thought it was pretty cool, and I say it whenever I want the lights off.  
I, along with many others here at GCU, enjoy your cards, and I believe you are having a lot of success with sales, so...don`t out`ten the lights, it obviously works for you.  
Hugs, Janet Lee
 
* What`s in the road..a head?  

Hi Tom,
 
Your caption might sound better reworded as others have suggested. No comas are neccessary. If you feel you want a resting place for the reader, you can split the caption.  
 
For example put *On his birthday*  above the photo and then the zinger on the bottom.  This supplies a little more punch.
 
The sales for the  month of May have been horrible for me too. Disappointing after sales were increasing steadily.
 
~Audrey