How to make a Toolbar representation bitmap for a UserControl??

Hello Every1,
I wanna make a Bitmap for my usercontrol so that I can change its representation in the toolbox. But the problem, is no matter how big the bitmap i make, it cant be displayed properly in the VB Toolbox. Its displayed but nothing can be made out of it. I want to make one just like the Label control, what dimensions should i take for the bitmap and what format should i save it in.Thanx in advance.

Toolbox bitmaps are shown at 16*15 pixels. The bitmap you set will be scaled if neccessary.