I've been working on backing up any adverts and promo videos I see on Youtube, just started really. Found some interesting ones just today:
Japanese Dynamite Headdy commercial. I love when they do these clay animations for ads.
Sega Video Magazine Volume 8(?) Part one and Part two
Has some interesting little animations (done on a computer by the looks of it) of Sonic based on the old concept art, as well as I think early Sonic Cd footage. Only thing that makes me think it's early is it's using the unused title screen music and for the time travel bit it's using that first track on the CD instead of the sound effect they went with.
Virtua Racing UK commercial. Been looking for this one for ages. I love the batshit UK Pirate Sega ones, seeing as I grew up on those.
The whole account has some British, Spanish and more Japanese promo videos, including a Saturn one that uses Arcade footage, tut tut!
There was an excellent long video on Youtube some time back that was some kind of educational video about 'the power of advertising' that focused on Sega that had commercials, merchandise, the tour buses, even radio show competitions with Sonic CD music in the background. It really showed just how hard Sega blew their money on advertising back then. Sadly it got pulled and I haven't seen it re-uploaded anywhere.