Caution Labels for Carton Boxes
They are warning labels commonly found carton boxes. This image has a transparent background which can be used as an alpha channel.

If you are planning to create a carton box 3D model, you may want to consider Carton Box Cardboard Texture (Paper 0025) and Glossy Brown Duct Tape Texture (Others 0011).
 
High Voltage Warning Sign Label
It is the classic high voltage warning symbol in yellow and black contrast.
Chemical Weapon Warning Sign Label
It is the chemical weapon warning symbol in yellow and black contrast.
 
Radiation Warning Sign Label
It is the iconic radiation hazard warning symbol in yellow and black contrast.
Biohazard Warning Sign Label
It is the iconic biohazard warning symbol in yellow and black contrast.