Using image and and controls in front

HI,

I want to use image and control in front I.e. taking existent image as background and put on it button ,list view etc.
I'm having blend 2012 and I try with adding grid and on it put image control and bind it to the image but its not working
since you cannot drag control to image,what is the right way to do it?

2. which image format is preferred in WPF (to support high quality image) ,is it bitmap ,gif ,jpg ?

Thanks,