Beautiful. Fun technique...I'd want to play like that if I still had a wet darkroom. It'd be hard to emulate with Photoshop: assuming a Diana negative, first steps might be to decide on a heavily textured paper and then modify/tone appropriately with Nik (rather than struggling with Photoshop). I've found deep selenium-brown tone difficult in inkjet prints though the printer itself does offer strong tone controls independent of Nik/Photoshop.