Doing it quick and dirty:
Select first column as V-BLOCK. Then press 40I<space><esc>, where "40" is number of spaces you want to add to center the picture.
Or you can use :h v_> to shift by any number of shiftwidth() to the right.
I don't think there is a built-in way to achieve what you want to do, so I decided to try to implement it by myself. I got a working solution but this kind of text manipulation has a ton of corner cases and they are most probably not handled by my solution. Hopefully that will give you some inspiration to code your own (better) solution. Also there might ...