Paul, I wrestle with that question internally. I think it's helpful to have a wide variety of pics, especially if there's an old pic, then a newer one of a same plant in better health. I've asked for a couple old pics to be deleted before, but at this point lean more toward leaving them up.
More importantly I think is the 'thumb thing.' As much as I might like a macro pic, I don't thumb them if that will cause the number of thumbs on that pic to make it the #1 pic, that shows up in the database listing. For that, I always try to vote for the most clear pic that shows the most of a particular plant, the ideal specimen with enough leaves/flowers/whatever to recognize the average plant by comparison. A flower macro is not what I prefer, but I'm sure there are those who would vehemently feel differently. Obvious exceptions would be something recognized only by its' flowers, like daylilies, roses, Plumeria, Hibiscus, where the only difference is usually the flowers of each cultivar and the leaves are pretty much the same for thousands of plants.
Also, no offense to you and your altruistic willingness to take pics in commercial setting, which are no doubt helpful since the 'for sale' version is what people can most easily recognize if shopping for a plant, but I also try to vote for someone's personally loved plant over pics like that. I hope you will continue adding these great pics, and I'm glad to have a chance to say why I've rarely thumbed any of them, and how much I appreciate having them available for so many plants. We can see the 'twig for sale' all the way to the mature plant, for so many plants. Thank you, and well done!!
But back to your question, if those are the kind of pics you would replace, that's worth doing, IMVHO. After enough pics to fully represent/recognize a plant, the others are just so much scrolling. If your newer pics show any detail or overall appearance not already in the older pics, I would just add them and not delete the older ones.
