No one had a photograph on a tombstone until less than 200 years ago. Goyim often had carved images on tombs but that’s very expensive (i.e. something for royalty) – Jews don’t hold by graven images.
A photograph on a tombstone will fade fairly quickly, and most people won’t tombstones to be fairly permanent. To make it permanent you need to convert it to an engraving which is very expensive and halachially questionable.