Yarp, the thumb is generated from the render. If you stop half way in the render and save there, the thumb will be half complete. And its not a thumb. If you rendered in 800x600, that's the size of the .bmp. The bmp is automatically saved side by side with the brx file and has no connection to it. For example, save a brx. Reopen it and change skyz and move the camera to a different postion. Watch the mini render window change, but don't render it. Save. When you reopen you'll see a difference between your scene and your mini view. So if you're looking for image data in the brx file, I don't think its there. As for renaming to a .png or something, that's a great idea. Don't overwrite the bmp. Lets say I render all night and don't export an image. The high end B5 render will be in the bmp. I'd hate to have that overwritten.