make your own header

do ya'll use picnik? if not, you should def check it out. I have used it before but never thought about using to to make a blog header til I came across a how-to blog post online today.
I made this one:

and love it! it was super easy: (here's where I read how) I also found a background that I want to use with it but I can't figure out how to get the header to be centered at the top, when I upload it- it aligns it on the left side of the top =\ any one have any ideas?!

I like my background now, and this its cute so I don't know why I'm wanting a new one already since I just got this one yesterday!

Let me know if you make your own header or anything- I wanna see !