As far as I know, you can insert the image as an Xref but you will be required to adjust the size thereafter.
Alternatively, you can copy and paste an image in MS Paint then use ctrl + C to copy the image from there and then paste it in the AutoCAD table cell using Ctrl + V. This will insert the image again in the cell but not as an Xref.
This second method is kind of like a workaround which you can use to insert images like company logo in title block without keeping it as an Xref.