Beyond that, there is little to suggest that Islam explicitly forbids art depicting humans. In the case of prophets though, I think it is discouraged (by muslims) largely to prevent misattributing features or misrepresenting them (and of course, mockery as well).
I should add, there is probably a bit of miscommunication when people use the term "Islamic art". Some may mean art that does not violate Islamic principles (whatever those may be to them), others may take it to refer specifically to the typical aniconistic style of art that has now become synonymous with "Islamic art" (at least that's what I, admittedly, thought of in my previous comment), or perhaps art originating from muslim territories / made by muslims, etc.
Just as an example, in sunnism even the grave of the prophet Mohammed (pbuh) is basically completely anonymous and unremarkable, to the point where you wouldn't know about it even if you were right in front of it. That's to avoid any grave worshiping, or ritualistic "pilgrimage."
Shiism, on the other hand, involves a LOT of rituals around saint worshipping, huge shrines, and important relics. Because of that, representations of saints and even the prophet are a lot, lot less problematic (and even mainstream, with portraits of Husayn being common in religious ceremonies). Even then, Persian art was historically even less restrictive than the mainstream modern shia tendency of not really representing the prophet itself anymore.
Now, you might say that this proves Ken White's point, but it really doesn't!. The reality is that for most muslims, sunnism being the biggest denomination by far, there is really no debate that this type of representation is completely forbidden. There is also virtually no disagreement on the subject between the different sunni branches (who usually are pretty similar in general anyways). The only rift is between sunnis and shias, but it is so wide that it makes no sense to even lump the two groups together in this conversation. It's not just a sectarian disagreement over interpretation that could be open for debate, it's almost two completely different approaches and beliefs.
So basically those "specific sects" would basically include 99.99% of practicing sunnis, all branches of sunnism, and every sunni religious authority. That's more than 80-85% of muslims, including shias. So there is definitely some universality of opinion here.