WebSaver+ let you download a webpage (including pictures) and stitch it together as a large image. 

Can be used from the share menu or copy url to your Clipboard. It save the webpage as one (long) image and saves it to the Camera Roll of your iPhone or iPad. 

You get a share menu pop-up after the new image is saved to your Camera Roll. This can take a few secs., so please be patient. ☺️