After some experimenting, I was able to create some branching dust patterns on a piece of ABS plastic. They bear a superficial resemblance to the dust patters in the photo linked to in the OP. A photo of mine can be seen here. I used a source of -15kVDC to create latent electrostatic patterns on the inside of the cover for my Casio graphing calculator, which had been cleaned of any oil and dirt and allowed to air dry. This isn’t meant to suggest the patterns asked about in the OP were formed in this manner, only that such patterns can be formed by static electricity. The OP doesn’t mention exactly how the blower was stored, only that it was in a box. Was it also wrapped in plastic, or supported in styrofoam packaging of some sort? If so, I’d suggest that the patterns were created at the time it was unpacked as a result of removing the wrapping or packaging, rather than there having been latent patterns on the surface at the time the unit was put in storage. I’ll continue to try to create patterns more similar to the ones see in the OP’s photo. I love science!