I have a post already started for tomorrow that is incredibly yummy and a must-try. But Jenny gave a great idea for a blog header how-to. I want to start by saying very clearly that I am no expert AT ALL in this area. I do not know HTML from WXYZ. =) But dear friends and sisters have taught me all I know, so my expertise is simply in following directions and being a copycat.
Do you know about Scrapblog? If not, don't say I didn't warn you that it's totally addictive. Scrapblog is an online, digital scrapbooking service that is 100% free. Visiting and setting up an account are the first steps. When you have an account, click the Create a New Scrapblog button to begin. From there, you can add all sorts of page elements like backgrounds, personal pictures, stickers, etc. To choose potential elements, just click on the button in the left-hand column, then click to add stickers, backgrounds, etc. When I started using Scrapblog, the amount of backgrounds and stickers was manageable to where I could actually scroll through them all to choose. I'd suggest you do a search to narrow down your choices. For example, if you want header with blue elements, do a search for 'blue.' I'm not impressed by their tags for their elements (when you search for something like 'dots' very few stickers are found even though they have countless stickers with dots), but it at least gets you started.
So play around with the system, design your header, then save your work. It will ask you if you want to publish your scrapblog. Click 'yes.' You do not have to choose to share your page, but it must be published in order for you to upload it to the blog. When it is published, go to File:Export as jpeg. It will bring up a dialog box with the pages of your scrapblog. Click 'download' underneath the page you want, then choose to save it. Remember where you saved it on your computer!
To make it your blog header, go into your layout section for your blog. Click to edit your header. Your blog title will appear followed by the description then image. Browse your computer for your scrapblog header. Then, make sure you click both the 'Instead of title and description' and the 'Shrink to Fit' buttons. Click save, then check your blog, and you're done!
I wrote this post quickly and off the top of my (tired, mommy-ified, decaffeinated, and non-showered) head, so it is very likely that I accidentally skipped a step. So try it out, and please feel free to ask questions. I'll do my best to help.