Oh, I'm afraid we don't have an API to create those. It should be fairly easy to do. Just put this in a cWorld method. Something like this:
Uint32 cWorld:SpawnPainting(double a_PosX, double a_PosY, double a_PosZ, eBlockFace a_BlockFace, AString a_PaintingName)
{
cPainting * Painting = new cPainting(a_PaintingName, a_BlockFace, a_PosX, a_PosY, a_PosZ);
Painting->Initialize(*this);
return Painting->GetUniqueID();
}