Wifi.ru — Moscow transportation system public wi-fi network offers branding of login / authorization page. I've done some customizations for several clients and here is for example authorization page for famous Russian pharmaceutical brand. 

There were some less scary and more funny approaches — they washed off eventually

There also were some funny ones bun they washed off too — we've found balance with some pumpkins and small witch on the background

There were tons of approaches — pumpkins, demons, sculls, ghosts and all that dark stuff. We finally get to stop on pumpkin creative with witch woman on the horizon. Not too kawaii, not too scary though.