Ever since Flash fullscreen within your browser was introduced, it has been used and abused time and time again but for good reason. There is definitely a time and place for Flash fullscreen.
Here are 31+ different sets of Flash fullscreen backgrounds. These Flash fullscreen backgrounds are resizable and of high quality available. Also, take note that many of fullscreen backgrounds listed are Flash animated backgrounds. These will will definitely give you an edge over others when it comes to your Flash projects. Enjoy!
If you are looking for a robust solution to managing your backgrounds in Flash be sure to checkout the Advanced Background Manager. This Flash utility handles multiple file types such as flv, swf, jpg, png and gif. Advanced Background Manager also allows for asset resizing and positioning in your Flash app.