Digital art Fan art Character concept Ninja Turtles Comic art Mutant ninja Teenage Turtles Teenage Ninja Turtles Dark background Teenage Mutant Adventurous spirit Thoughtful expression Character sketch Digital creation Ninja turtle Mutant turtles Ninja Turtles Teenage mutant turtles Mutant Ninja Turtles Fictional hero Ninja character Heroic posture Teenage turtle Turtles character Ninja Turtles character Teenage ninja turtle TMNT character Turtle character Fan tribute Pensive moment