I downloaded a deck from a friend and while I was learning the cards on my phone (android) everything seemed fine. The pictures had no issue.
But after syncing my deck on PC (Linux) and after the sync was completed, the pictures do not show up. It only shows the icon of an image but not the image itself.
If the image doesn’t show up when you review that card on AnkiWeb, it implies that AnkiDroid has not synced all your media to AnkiWeb yet. You may have more luck after enabling the new backend in the advanced preferences, then syncing again.