In order to convert a .bmp (or any other for that matter) raster image to a DWG format, you need to use some of the available raster to vector conversion solutions. Works best on images that contain geometry, shapes and similar. It is not perfect but a lof of CAD users try to speed up their work and convert image to a DWG or even DXF format.
Possibly can also be done in vector graphics software with raster to vector function, for example CorelDraw's tracing function or similar.