Can you please change the image on the 404 page to be less intimidating and scary? I can understand that a 500 error might be intentionally scary, but a rage.svg on a 404 page? That seems like overkill to me. Current page gave wrong ideas. People first reaction is something like "OMG, I broke something".

How about a sad Jenkins or shrugging Jenkins instead?

Something more like this:

Also a good idea in (in addition to image change add text when user is simply logged out): JENKINS-21813