There's a ton of PC Engine demo discs with all kinds of crazy stuff, including lots of Mode 7 effects, exclusive mini games and misc. The PC Engine Catalog discs 1 - 6 + Duo RX A & B are a good start. Most of these have the complete game of Nectaris on them. One or two(?) have Bomberman '94 Special Edition/Caravan/Taikenban. Catalog 4 has Force Gear.
The Seiya Monogatari/AFS demo disc has Cychorider on it.
There's the Tengai Makyou II/Dragon Slayer disc.
Deden no Den is a stand-alone Bomberman '94 demo with everything replaced by Kabuki Danjuro.
Motteke Tomago only exists as a demo disc.
There's an Emerald Dragon taikenban (like most, it's not simply a short gameplay segment).
There's a Fuun Kabuki Den taikenban, but it's more of a straight segment from the full game.
Snatcher Pilot Disk has a bunch of exclusive assets.
All but the stand-alone Bomberman '94 taikenban (unless the title begins with a different name) are included in the "Turbo Grafx 16 CD PCECD Complete CD-ROM Collection" torrent.
Since demos like the Special Version HuCards weren't sold commercially, I don't think that you should nitpick enough to not just play them on the Everdrive.