SeedRandom[3488];
AbsoluteTiming[
 directBlendingImages = Table[
    RemoveBackground@
     ImageAdjust[
      Blend[Colorize[#, ColorFunction -> RandomChoice[{"IslandColors", "FruitPunchColors", "AvocadoColors", "Rainbow"}]] & /@ RandomChoice[mandalaImages, 4], RandomReal[1, 4]]], 12];
 ]