While we’re discussion images, my view is that some basics would be useful.  For validation, things like:

Is it an image?
Is the size between this min and max?
Does it have the right number of color channels?
Do the pixels have a minimum level of variance (for example, did we take the lens cap off?)

For feature engineering, things like:

Gaussian blur
Grayscale
Sobel filter
Canny filter

Do you think that would be valuable?