I have been storing pictures in a shared google drive and then using the link (with some modfiications) to access the picture. It doesn't always work. Where do you like to store images?
Separately if you are not writing a scientific book are you still using LaTex or just Pandoc?I feel like I am often inserting HTML code in order to center things, have line breaks, when I am using just Pandoc markdown.
I guess the hardcore way is to store images inside the HTML document as data URIs (--self-contained will do that.) It used to be frowned upon to store images and documents on different servers, not only because of the loading delay but because when people linked to other people's images they effectively stole their bandwidth, apart from any rights in the images as such. I'm not sure how much of a problem any of that is nowadays.
/bpj