Detecting face like patterns using CNN based face detector I have a CNN based object detector trained on WIDER Face dataset. It can successfully detect human faces in a given image.  

Now, I am trying to detect abstract face and minimalistic face patterns in clouds or houses etc but having no success. 

Initially, I thought I could lower the detection threshold to detect such patterns, but such scheme didn't work. 

My question is there any way other than collecting and labelling such training examples (face like patterns) to solve this problem.
You probably need a training set that contains examples of abstract faces and minimalistic face patterns.  There's no reason to expect a neural network trained on real faces to detect abstract face patterns; neural networks don't necessarily generalize that way.