I'm working on my first practice site since I started properly studying css (it's a site about dog food/dog treats). I've run into a barrier: I don't know what to do with the header.

I'm just looking at a boring rectangle-block header above a typical two-column page. I'm stuck for ideas of how to make a good-looking header. Will I have to use image editing software to draw my own graphics to make it look good, or does anyone know a site where I can get header graphics? So far I've only seen sites for photos and icons. I know that headers with graphics that appear to flow/overlap into the main content below tend to look good, but I don't know what to do with that.

Ideas for headers, or tips on how to conceptually think about headers so that I can come up with my own ideas?