The FAQ page:
Q: Can I customize the design of the blog?
A: Yes. If you don’t like the themes provided with BlogEngine.NET, you can change one so it matches your needs or create a new one from scratch. It requires only basic knowledge about ASP.NET and HTML to create a theme. Read more on
theme creation/modification here.
The above link seems not correct. Sould be http://razorant.com/blogenginewiki/ThemeCreation.ashx instead of http://www.dotnetblogengine.net/wiki/ThemeCreation.ashx