Daz renders are pictures, and they are just as much traceable as any other pictures.
I don't know anything about Daz including covert watermarks on thee pictures and that would not make much sense or meaning for them to do. If they did it, I think it woud be known already.
Considering daz content, as much as I heard from complaints of content producers, Daz does not give a fuck about piracy as there are plenty of 3d content sites and nobody cares. Nobody even bothers to complain about that. So that's one more reason why they would not do it. It seems that payment is totally voluntary here.
To add to Onix's post, most images contain something called EXIF metadata.
If you search for 'EXIF metadata editor' you'll find some apps that might help you. Or search 'Remove EXIF data from pictures'. Fair warning, I haven't tried any of this, and I don't use Daz.
This counts as tagging possibility, but DAZ does not ad any EXIF data to the picture and if it exist it is on the plain view, any image viewer will show that information