Open the tif in Photoshop, go to the Image menu, select Mode, choose Bitmap. Save and Exit Photoshop.
Now, when you insert the tif into Autocad you will have a black background with white lines. You will also now be able to click on the image boundary, open Properties and under the "Misc" section, turn on Transparency. This can be helpful when trying to position the image precisely over the top of an existing drawing.