Pacific Northwest Legends: A Natural History is a 2015 mural project in Spokane, WA by Justin Gibbens with assistance by Will Bow that includes a panel dedicated to the Pacific Northwest Tree Octopus (and obviously inspired by the poster I made):
Image may be NSFW.
Clik here to view.
There are 7 other panels, 7 x 17 feet each, that showcase "historical and contemporary cryptids that inhabit the collective imagination of the Pacific Northwest", including: Sasquatch, Thunderbird, Skin-walker, Pacific Merman, Ogopogo, Jakalope, and Ozwald the flying monkey.
The mural is under the BNSF rail tunnel on S. Post Street (Google maps link -- Google's street view doesn't currently show the tree octopus panel very clearly since it's along the lane Google's car didn't go down).