They also seem to be posting links on pinterest, youtube, etc. and they are pulling in about half a million visitors per month, that's not a small deal.
The domain holder is hidden and the host (https://www.name.com/) seems not responding, its probably going to demand some investigative force to find this individual? Its someone appearing to operate from US so that is something for (https://www.justice.gov/criminal-ccips/reporting-computer-internet-related-or-intellectual-property-crime) for those affected in the US.
Most country's have international treaties regarding cybercrime but you first need to get proper local authority's informed about your case so that they can call upon these treaties for requesting information. For EU members you can find links to your local cybercrime unit here (https://www.europol.europa.eu/report-a-crime)
If you want more information regarding your possibility for deference against this type of crimes then visit (https://www.export.gov/article?id=DOJ-Computer-Crime-and-Intellectual-Property-Section-CCIPS) for US members.
And (https://euipo.europa.eu/ohimportal/en/home) for EU members.
PS: Sketchfab staff is pointing DMCA take-down notice/requests to desirefx.com and mail Graphics4pro@gmail.com but its not clear jet that this is the same individual that owns desirefx.me (that website does not provide any contact info). The .com version seems valid, the .me version seems copy (has same but free wordpress theme).
Sketchfab provides a handy tool to help create a DMCA notice (https://docs.google.com/forms/d/e/1FAIpQLSfK8PodZ67kAKwjRBdvjZEMf7EEHfHUu7-nPqbURwk2LvPf-w/viewform)
It would be nice CGtrader also provides something like this?