what do you mean with preview?

do you have click to load original image enabled in your privacy settings?

if not, did it show the raw link first?

when you load a page, the client tries to detect which links are images. it looks at the URL and if it ends with an image extension, we assume it's an image. if not, we just try to load it as an image in the background. it shows the raw link during this time. i notice that myself sometimes.

so if a link was detected as an image, it tries to use the processed images first. if we didn't process them yet (we do that in the background now since it used to slow down posting and commenting), we fallback to the original image. we also fallback to the original image on error - again, assuming you don't have click to load original image enabled.

if you do, then we always show an image containing the text "processing ..." (if it's still processing) or "click to load" (if there was an error with the processed images) first. you can click both images to load the original image.

regarding the loading, we don't have a "loading" image or anything else to show that it's loading. i tried to do something like that but that was another whole story on top of fixing the processing and fullscreen, lol

so i left that out for the next iteration :)

Oh, if you're on iOS, I guess this is what @k00b meant here