I love this colourful spotted paper I found and created a multicoloured Happy Birthday card around it with a blank inside. You should just be able to print on a standard 8 x 11 paper and fold it in half. Please let me know if you have any problems.
And I also created a similar version with a solid colour text. You can download it from dropbox for free.
And you can also check out this round-up of my favourite free printable Birthday cards that I have found from other fabulous bloggers if you are looking for a different style Birthday card.
So please tell me what you think, and if you want them modified in any way I will definitely try my best to get to it as quickly as I can.