How to find the source of image if reverse search fails?

[UNDFTD]

for my next project for class, I have to design a simplistic game which gives a more or less, yes or no answer. My plan is to create something that follows 'The Higher Lower Game'. And for this game to pass as an project, I need to find the source of a couple of images.

My question to you guys is: What do I do, or what are some of your tips to finding the source of the image if the reverse search image fails upon you first time?