Though you can design your blog anyway you want, blog traffic can be influenced by the actual design of your blog. Though I haven’t changed the blog design on this blog for over a year, I’ve experimented with other sites such as SampleADay.com and CanadaSamples.com and seen positive results after changing the design to something more professional.
You can win a reader over with your blog content, but to get them to continue reading, you need a blog design that doesn’t look spammy or unprofessional. By adding your own custom design, you can help make your blog design look more original and credible. On SampleADay.com I even added my own Avatar of myself for a more personal effect.
When it comes down to it, free blog templates are cheap, but they make your blog look like everyone else’s. If you are getting decent traffic, pay for a professinal design or at least design it yourself.