You can post your screenshots there without an account. You will need one to start a thread, however. NOTE: The site does have a problem with creating an account in MS Edge. Works fine in Firefox. Let me know what you think about it http://bngscoreboard.do.am/forum/
Theres been no place specifically for competing in scenarios. I'm suprised that the team hasnt done that yet.
There was the Scenario Time Megathread, but the problem with that is it's an excessive amount of work for the thread creator to try and maintain a list and fill out info for many dozens of scenarios every day, and to separate them by version number so the competitive balance isn't destroyed with every update to the game. If you want early leaderboards before they're officially implemented (and with how many of these kinds of threads keep showing up, it seems a lot of people do), the solution isn't many dozen separate threads on a different forum. It's some kind of speedrunning wiki setup where people put in their own records, version number and picture/video proof so the only external work needed is someone verifying the pictures/videos every once in a while, and where the records can be sorted by version number. In a quick search, found an example of something like this: http://www.cyberscore.me.uk/game/31 That idea might work, or maybe a simpler editable spreadsheet of some kind where people can submit their own data. Either way, there's always the risk you'll go through all this effort to set this up and then the devs release leaderboards a month later. Though believe me, I'm itching for some leaderboards too. That's one of the reasons I'm maintaining my own personal leaderboard thread in the videos forum besides just wanting to have quality runs of every scenario on YouTube eventually.
Well, this is my view on how to maintain and/or create leader boards for the time being: http://www.beamng.com/threads/canyon-race-time-trial-leader-board.29958/ It's for one scenario only, but by using google forms in combination with spreadsheets its a lot more user friendly in my opinion. The only thing that I need to do is go to the spreadsheet and post a picture of the top players by sorting the time column. And the user gets a nice form to fill in.