I re-implemented the old orthographic voxel / pixel editor that worked in Java 5 years ago in C++. The new editor works with both pixel art and voxel chunks, using the same file format for both. It exports pixel art as PNG's again and turns them into sprites and wall textures. As you increase the level, you go higher in whichever axis you face and vice-versa. In voxel mode, you set texture. In pixel mode, you set color. Loaded as voxels in the game, the color information turns into vertex lights.

Source: https://github.com/dimitrilozovoy/Voxyc/blob/master/editor/OrthoEditor.cpp

App: https://play.google.com/store/apps/details?id=com.voxyc.voxyc