Picnik is a great photo editing website, which I had the stroke of genius to use to create a new header. Lindsay requested a tutorial, so here it is!
1. upload a photo: First you have to decide if you want a solid background, or a picture as your background. If you don't want a picture in your background, it doesn't matter what picture you upload because you are going to change the settings so that the picture disappears. If you do want a picture background, you don't have to follow these steps.
2. edit: Choose the exposure tab, then select contrast and drag it to -100. You should see a gray background. Click ok to save your progress.
3. create: Now comes the easy and fun stuff! In the create tab, scroll through the featured effects on the left hand side. Select tint. This will change the background to the color of your choice. Hit apply to save your progress. Once you do that, you can add text, frames, borders, or whatever you want!
4. save & upload: Select the save and share tab. I changed the file name so it would be easy to find. You might want to play around with the size (edit tab/resize). I wanted a more rectangular header so I did 700 x 300 (make sure you un-check "keep proportions").
See pretty easy right? Now you are ready to upload to blogger! Hope this helps!