Design error pages

I feel like I have seen an issue about this before, but 404 pages (and other error pages) need design. They are located in app/cake/src/Template/Errors/error400.ctp and .../error_500.ctp. First of all, they contain $this->layout = 'error'; which should probably be removed, as error pages probably should have the same layout as other pages. Second, if that is removed the text needs some extra styling. You can test a 404 page by going to http://127.0.0.1:2354/artifacts/0 (or just http://127.0.0.1:2354/nonsense).