I designed a few and it turned out great (That's for me, anyway) the very first that i made that i like so much is my other site's header clickdtalk then next is my hubby's site IMW ever since he started i designed, re-designed he's site and header. I really love playing with images and making my own headers.
I have downloaded and use a few graphic editor software, an image manipulation etc..., and i would like to share them to you this are a Free to download software and also a very easy to use.
Serif Draw Plus 4.0 - Vector Graphics, Illustration and Drawing; This is my one of my favorite...you can create a vector image and even an animation, you can convert the image and edit them so easy to learn and you are going to enjoy using this software.
Gimp - This is another Popular image manipulator, you can find a lot of tutorial that can help you with this software. Honestly, i downloaded this but have not tried it yet, i read a lot of tutorial and the reputation is quite high so it's all up to you but for me it's worth trying...i am definitely will try to learn how to use Gimp.
Inkscape - An Open Source vector graphics editor, If you can't afford Illustrator, CorelDraw, or Xara X, using the W3C standard Scalable Vector Graphics (SVG) file format then inkscape is the answer it's capabilities is similar to the above mentioned. I love this and i am studying on how to trace my own image.
Show you one that is done 100% by inkscape by one of artistic user ScislaC
How do you like that!....
Anyway, this are the three that i know except Adobe because for me this is for professional users you have to pay i love to have one but i am a basic user so i am happy with what i have. Now that you have this choices of image editor software (Actually more then editor) you can start playing with your images and make your own site header.
Please let me know which one you choose and enjoy to use among the three, i would love to hear them.