Hi, this is going to be a dumb question but here goes. I am a designer. I work primarily in Indesign, Illustrator and Photoshop. I am being asked to choose images for my work's web site that is being developed. It is a hefty web site with literally hundreds of images needed. However, the ladies building the pages, the administrator don't want to show me how to place the images into the design. They want me to scroll through the beta website and pick photos that I think will look best. Im finding this difficult to do. I really need to see how the photos look with all the elements, and how it flows, the cropping, the story they tell... etc. Im wondering if this is usual protocol for web page building? 

No it's not. But if this is how they want you to do things there's not much you can do about it.

If this is not the usual protocol then I can ask with more confidence to be taught how to place images myself.

I need to make a good argument, state a solid case, in order to inform them that the way they are asking me to do this is not efficient. They are learning as well. 

Any pointers?

In order to choose the most appropriate images, you need to know the page content, its no good having a dog image that is supposed to support the text about a cat.

Secondly, you are correct with the image flow, I hope they are not so different though that some of the image styles are not the same of others, that would be insane.

^ Indeed - if these are images that are relevant to content then they should be the responsibility of your authors to source.

Saying that, if you're being asked to provide assistance in helping authors choose the best images, best cropping positions etc. it does sound as if they are seeking your professional opinion. It's nothing to with design per say, rather your trained eye!