1) A transparency block,
see when using a background like this
It would be cool if you could hide the icons that are "behind" the logo.
2) Oval re-shaper
When picking a back ground, its often hard to find one that fits the orientation of the slider dock circle. Thus I suggest a way to reshape the oval to your needs.
The way I imagine it working is similar to mircosoft word's oval drawer, where you click and drag your oval and then can reshape it with the ovals.
(It should be noted that I know nothing about programing, so I have no idea if this stuff is possible. I'm just a guy with some ideas ^^;)