I use a software call PureRef, it allows you to make like a canvas of multiple images and quickly check them, I highly recommend it. To my surprise, it is remarkably fast, even with a huge amount of picture in it.
You can even save your ref file with all the pic in it, so you could have, for example a bunch of maps that you check for reference for a particular subject, lets say deserts. Whenever you want to check those, just open the software, pick the file you wish and voila, all the pictures/maps are there.
My explanation is pretty terrible so here is a link for you to check it out.
https://www.pureref.com/
Beside that it's just a well organized system of folders and sub-folders for me.