The NIRVANA+ Engine is a 'bicolour' (multicolour 8×2) graphics engine written by Einar Saukas, supporting a multicolour area of 32 character columns by (at most) 23 character rows. It's open source and royalty-free (even for commercial programs). Further details can be found in this thread. The latest version is available for download here.
List of games currently under development (with released demos):