The NIRVANA Engine is a 'bicolour' (multicolour 8×2) graphics engine written by Einar Saukas, supporting graphics using 22 character rows and 30 character columns. It's open source and freely available (even for commercial programs). The latest version can be found here.
It natively supports all standard Spectrum models (48K, 128K, +2, +2A, +2B, +3).
List of released games using the NIRVANA Engine: