Methinks we have different definitions of the word 'cool'... since wasting bandwidth on animated nonsense on a error page is so mind-numbingly... well, I lack the words in polite company.
Made all the worse by the current page's glut of "JS for nothing", meta tags no legitimate UA cares about particularly on a 404, classes on elements that have zero reason to even have classes, preloading link nonsense wasting the user's bandwidth, empty title attribute, and 5.8k of minified markup doing the job of around 1k of code!
You'd almost think it was slopped together with the train wreck laundry list of how NOT to build a website that is bootstrap.
But given the wording of the request, I shudder in horror at the monstrosities you are likely to get out of this "competition" given the request for animated trash... though what would actually be useful to users in such a page would be to simply have the 404 be the same template as the rest of the website! Same sidebar with normal navigation, showing the user, votes, followers at the bottom... same background, same left side bar that scrolls with the content, then plug in the error message into the center column with those same helpful links.
NOT some bloated trash animated nonsense.
Not exactly what I thought you were talking about for 'contests' -- particularly since if I were to make an entry it basically involves rewriting or recreating the site itself. Though it could use it what with the nutters 105k of markup without the content even being loaded filled to the brim with "JS for NOTHING" that tells large swaths of potential users to go plow themselves. Again, I know a number of people who would be interested in this site if the over-use of CSR mated to massive bandwidth bloat didn't tell them where to stick it!
The voting counted on the day submission ENDS is also pretty hinky, especially with the "please spam the devil out of it" plea. Actually comes across as pretty sleazy overall.