Today a new group (Kalisto) released it's first DC backup image. The game is named "Evolution: The World of Sacred Device" and as the nfo file says:
Just before the arrival of the 8th Imperial Army, the player takes control of Mag and Linear and they fight their first battle, then search through their first dungeon. You'll meet and fight giant rats, giant caterpillars, and much more. A full review can also be found at: http://dreamcast.ign.com/reviews/11038.html.
This game will fit on a normal 74 Minute / 650MB CD. Have fun with our first DC release, and DON'T look for more soon, Just be happy if you get it..."