how I made my header by the time you get to the end of this, although I'm glad you did cos I like talking about pictures, and it gave me something to post today :-)
1.Make a background that is the size you want your header to be.I use Digital Image Suite, but you can use any image editor,like Paint.
2.Because I want the words to stay while the pictures change I added them next.
3.Having decided what pictures you want to use, you can crop them, add effects, and finally add them to your background
4.Repeat step 3 until you have a full background. Save the picture.
5. Repeat steps 3 and 4
6. Repeat step 5 :-p
7. Keep going until you have all the pieces you need. For my header I made 8.
You then have to animate it. I have an animation program on the computer, but you can use a website like Lunapic which has some great effects. You just need to upload the different pictures for your header and play until you get what you want. To make it work on blogger you have to put it into photobucket and get the html code. Just uploading it to blogger will give you a nice header, but a static one.
Nothing to it really..if I can do it anyone can :-)