Deral is a visual riff on Dural, the final boss of SEGA's Virtua Fighter games.
When the game was shown at Tokyo Game Show 1997, only a simple non-textured arena featuring two tiers and slopes between them was available [src]. Credit goes to Alex's Bomberman SS Shrine for the information and screenshot.
SEGA Saturn Magazine Vol.34's coverage is all on this unseen stage set on a four-tiered 14x14 pyramid, that resembles nothing in the final game. Even its background isn't used anywhere!
The same issue features a slightly different character select screen; Kurobon's icon is facing the wrong way, and many of the character icons are cruder-looking, including Baguro, Combatant #12, Golem Bomber, Pegi Jr., Radibom, Denta and Pump. It's hard to see, but the backdrop is cropped from promo art of Saturn Bomberman.
A rough doodle of Bomberman. Found near the end of the "PLSCHR.BIN" file, where the graphics for the character select stored. No known palette, so the colours are approximated.