How are these guys getting 300+ backlinks to images per day?

Lawnstarter [dot] c o m is in a similar niche to me, but they have been going gangbusters lately. They are getting 300+ new backlinks per DAY! It only seems like recently their strategy has changed. A lot of their backlinks are going to images and are linked to from Blogspot blogs. I am assuming a PBN, but how are they getting the volume of backlinks? Have a look in ahrefs and let me know what you think?