If you have a scaled up canvas decal and stand next to it, the decal texture gets drawn over your weapon’s viewmodel as well. Doesn’t occur for some materials on weapons, like those with some kind of shader applied (i.e. transparency on the water gun, metal detector screen, entirety of the tower glove).
Stand next to a large canvas decal while holding a weapon in your hotbar.
The decal doesn’t affect the weapon viewmodel.
The decal affects the weapon viewmodel.