Type of images used to train a neural network
You should read this post from the same author. It is about how to build a learning dataset with Google's search, some javascript and some python.

The idea there is to collect as many pictures of the object as possible (object = banana) and then let the deep learning network to compare and learn to differentiate them from bulk random images from some free database.

I suppose background or partial image variations are all ok. You cannot know which part of the object is visible when the whole bunch is evaluated. 

Data needs to be fit to same size, at least Adobe has some tool for that.