You can use your own custom template. SBI has two ways to upload content:
- Block Builder - which is an uploading function for dummies, but still gives you enough flexibility to have an interesting site with images and ads
- Upload Your Own HTML - which is for intermediates and above, you create new pages from your template in any HTML editor (Dreamweaver, Front Page, AceHTML, etc, etc) and upload the whole file
The only thing I'd say about getting your own template is make sure it's relatively simple (little or no Flash) and SEO-optimized. That's not just for SBI, that's common sense for getting ranked by Google.
I got both my SBI templates
here, my partners company now makes them for SBIers. Also check out the resource centre at SBI, there are other templates you can buy quite cheaply.