To insert a raster image into a DWG file so that there is no need for an external image file:
- Open the raster image in an image editing application, such as Microsoft® Paint.
- Click Edit menu > Select All, or press CTRL+A.
- Click Edit menu > Copy, or press CTRL+C.
- In AutoCAD, click Edit menu > Paste Special.
- In the Paste Special dialog box, select the options Paste and Picture (Metafile) and then click OK.
- Place the image in the drawing.
The raster image will be embedded in the DWG file as an OLE object and will be saved completely within the DWG file.
Source: Autodesk Knowledge Network