When a feature is so popular as it is, we have been cautious in doing anything that might disrupt how the feature works, how easy it is to use and the visual look of it.
However, 2 wishes has been frequent since Speed Dial was created. One is the ability to have more than 9 sites in the Speed Dial, the other is ways to improve the visual look of it using a user supplied background picture.
Your wishes have been heard, and I'm happy to present the new configuration dialog for Speed Dial, available from the bottom right corner of Speed Dial:
As you can see from the screen shot, you can now set a background image, set that it should be centered, stretched or tiled.
You can also see the layout of the Speed Dial from 4 ranging up to 25 sites visible in Speed Dial.
Hope you enjoy the new features in Opera 10 beta 1, and don't hesitate to offer constructive feedback or suggestions on how to improve this aspect of it!