just a stab in the dark Martin…but perhaps you could cut a sandblast mask on the plotter and then have them sandblasted…sorry…I don’t do blasting but it just struck me as a possibility…might depend on how many and how deep a relief is wanted for the image?
I’m sure someone else will take this up or suggest otherwise…or tell me to shut up!
i had a customer ask of that once.
what we did was to cut a logo in 1" thick foamex (all in once peace). then when the slabe was wet it was pressed into place. the slab was left for about 30 mins then the logo removed. the cement was still wet but firm. then it was left to harden. they looked great.. & he ended up with them all over the place on the grounds of his garden centre.
i know this was done when creating the slab but maybe you could get him to do somthing the same.
Sandblasting is the way to go here unless you go to a stone mason, the sort of people who will do your very last sign !!
paint the area to provide adhesion for the mask , then when youre done just blast off the paint