This page of the guide to Assassin's Creed Valhalla Dawn of Ragnarok contains the location of all the Cosmetic Schemes available in the Gullnamar region.
Location: Onarthorp, to the right of the harbor.
This diagram lies on the wooden table, right next to the contested building where you will find the resource chests.
Location: southern part of the map, near the edge of the regnion.
This diagram lies on the small mast of a destroyed boat. Climb there to grab the item.
You will find the diagram in a small cave, on a wooden platform. Just climb on it to get to the find.
The diagram lies on a wooden desk, and to get to it, you have to go through an open window. You will climb up there without a problem.
Location: Fornama Dig Site
The diagram is hidden under the building. To get to it, you must destroy the two crumbled walls. The Incendiary Powder Trap ability will work best for this purpose. However, if you don't have one, there are quite a few vases of flammable substance lying around.
Location: northern part of the region, right at the synchronization point.
You will find this diagram in the lair of the wolves. It's best to eliminate the whole bunch so they don't interfere with picking up the object.