So just a quick test…
Created a new Illustrator document with an artboard measurement of 4.25" (to mimic tile) and then 8 artboards.
Then go to Object > Artboards > Rearrange, to put them into a 2-row format
I then picked an image I made from a friends wedding that I had on the desktop and placed it in the document. I didn’t like the crop with 8 boards (it cut the people in half vertically), so I duplicated 2 of the boards and rearranged again for 2 rows.
I then went to File > Export for Screens > Select: All (which exports all of the artboards and numbers them)
And now I have 10 separate, sliced images that I can engrave on individual tiles.
That’s the easiest, most inefficient way, probably. But it works.
You could extrapolate the size of multiple tiles that will fit into the Glowforge bed/engravable area and set your artboards up that way - and then load the tiles correspondingly and make a larger engrave all in one go and then do the next one. That would be more efficient in the long run.