Implementing Dropbox features in a custom file explorer: API limitations for desktop apps?

Здравко Greg-DB Thank you for your replies, I think I can do better explanations. Like Windows explorer and mac finder, my file browser also displays files in a grid layout with thumbnails representing each file. When users are visiting the dropbox folder in my file browser, ideally, I would like to display small image thumbnails for image files. Although I can create thumbnails by analyzing the image files themselves, this can be time-consuming and take system resources, and it will trigger dropbox to sync down the files set to online-only by users, which isn't ideal. Since dropbox already generates thumbnails for such images and can display the thumbnails properly in windows explorer, I am wondering if my app can do the same - requesting existing thumbnails from Dropbox API(without analyzing the file and generating the thumbnail on my side), and without asking users to authorize via OAuth. This means, are there ways to acquire thumbnails available locally? (not by requesting from online file mirrors)

I hope my question is clear enough this time. Thank you all in advance.