Put a fly in your scene, nothing more natural, usual, persistent and inevitable than a fly... Your renders need flies!
This product comes with 2 blend files, one with blender hair and procedural textures and the other with the hair converted to mesh and baked textures.
Update:
2 new files with the flies rigged in hair and mesh modes and with 6 useful poses included. You must activate the Animation: Pose Library addon in your preferences tu use the poses.
Materials
3 Different PBR materials, domestic black, green and blue, with procedural and baked versions 10 4096x4096 texture files
Tested in Eevee and cycles
Polygon information (each fly in mesh version)
Verts: 13255 Faces: 8898 Triangles: 17662
OBJ and FBX files exported with blender default options
Brush away flies, if necessary....