Twitter - Scalable Backgrounds?

Not that I am aware of... as Twitter will only accept the standard raster file formats... er, and last time I looked, it wasn't accepting all of those due to some 'temporary something ot other'.

The trick is to come up with an image that looks good however it's cropped. Now there's a challenge. Most Twitterer's - even a lot of the designers fail. It makes me wonder how many people must browse with their bowser windows expanded sufficiently to see all the 'business cards' in the top left. Odd notion that one. I personally browse with the browser window, well a maximum of two thirds of the width of my 15" Macbook Pro monitor - generally smaller. I see very little of the background once the fixed width of the Twitterer's stream is accommodated - certainly never see their 'business cards'.