Try Guessed's suggestion with the triangle(s).
I hope I have interpreted his idea correctly.

First remove the top two images and file extension letters from cell 1 & 2 as well as the letters in cell 3.
Insert an 'Isosceles' Triangle and resize/position over the stamp image remaining so it is the same size or slightly bigger.
R/click the triangle and change the Outline colour to black and the weight to say 2¼ (experiment).
Fill > Picture > Navigate to your stamp image.
When you are satisfied with it, change the wrapping to In Line with Text.
Now drag up to first cell.
Delete the image in cell 3.
Press the Crtl key and hold, then drag down the image to cells 2 & 3.
R/click the image in cell 2 > Fill > Navigate to the reqd image.
Repeat for cell 3.

Try a print out, again for a comparison.



The triangle > Fill > Use your stamp image can of course be created independently of the document I have used in the video. It's probably better to do so and you can make it larger and then use/resize that one in a table cell.