The Flesh Tearer icons on the fenders were made using Greenstuff. I am no modeller, using greenstuff is something I've always struggled with. There's a trick to it, which I haven't learnt yet.
I had the work done by a user named PaganFoam, check out his youtube channel here: www.youtube.com/user/PaganFoam/ I don't know if he is still doing painting/modelling commsions, but I'm sure he'll be accommodating if you contact him.
Some more modelling work of his is seen in the Sanguinary Guard models.