So you have this logo, or background picture, you want to insert in your DWG file: unlike full AutoCAD though, you cannot Imageattach the file as the command does not exist in LT.
Simply open the Image file in another program/viewer, Select the entire image inside that program (if you cannot, you need another program/viewer application), then use Windows Copy/Paste ability to paste the image in LT.
For Raster Image files like JPEG or PNG or GIF, you can use Windows' own Paint program to do this. Make sure you do not insert the image on a layer set to no-plot.
Example: Open Windows Paint, using the File Pulldown menu in that program, open your raster image file. In the Edit Pulldown menu, use Select All to select the entire Image, then select Copy from the same pulldown menu.
Click over to LT, Select the Edit pulldown menu, Select Paste Special... (or type PASTESPEC) and select any Image or Picture selection that best meets your need, and continue with image placement.
The above method also works for PDFs (using any PDF Viewer with selection features similar to Windows Paint described above), TIFFs, Word/Excel and so many other programs. You are only limited by your imagination, the 'other' program's selection methods, and your choices of PASTESPEC command's pop-up.