End-to-end ML project walkthrough
Depending on the images you used but I would not necessarily convert them to greyscale as there could be vital information in the colors of the image when it comes to making a prediction.

Feature scaling is not necessary for any of those algorithms but they could perform better with it.

Yes you should plot the Receiver Operating Characteristic and the Area Under the Curve. This is a metric you should be using as your problem is about Binary Classification.


The rest looks good.