Control/Form background image performance as a function of image format/size

Hi all,
A few quick questions regarding background images for forms/controls. In ALL cases I'm looking for the best performance in rendering at form load/ switching between tab controls etc.

1) Does the raw format matter? i.e. is there a performance boost from using bitmaps as opposed .jpg, .png etc.? (I'm assuming there would always be a hit if you grab a picture at run time and set it to the background, but what about if you import a resource at design time?)

2) Does pixel format matter as well?

3) Should background image layout be set to tile or none (none is my intuition)

4) Should I always draw for exactly the size of my control? (Even if there is blank space around the border; obviously in "None" image layout)

5) If any of these things do matter, please post what, in your opinion, is the best format etc. to use.

Thanks!
Nick