You can also manually edit the CSS, and php text files ,which Artisteer creates when you save it, with a text editor like notepad or by using the built-in text editor in the Appearance section of WordPress' Dashboard.
Knowing how to use PhotoShop and Gimp to make high quality pictures can make your blog look great.
If you are wanting a decent theme instead of trying to make your own I would recommend paying for a premium theme. I can make my own themes but not to the standard of some of those out there for as little as $50 bucks. So it might be worth just buying one to your taste.
The Thesis theme is a great customizable drag and drop style theme which also is optimized for Search Engines by Chris Pearson. http://diythemes.com/ .