I've seen this done so I know it's possible. I want to place a flash 'movie' in the same spot as a jpg. So that if the visitor has flash turned off, that they will see the static jpg. If they have flash, then the 'movie' would appear instead. I don't know if it's javascript or just css with layers or maybe there is more than one way to make this happen. I'm all ears.
You can put your Flash movie in a div with a GIF or JPEG background image that is essentially a proxy for the Flash movie but Flash always draws a white rectangle briefly first before it shows any specified background colour so you can't completely eliminate that 'Flash' of white. Here is an example http://www.harvestpointecc.com/