Almost all datafeeds contain links to images, located on the server of the merchant, a CDN or at the networks servers. You might want to host the images on your own server:

1. A lot of external images might be a trigger voor google
2. Sometimes the images are ridiculous large
3. Even with images of decent size, resizing them using an image library like GD gives better quality then using  html/css

Fetching the images during feed parsing is not a good idea, it will take a lot of time, and with a bit of bad luck the merchants server will block your IP for abuse. A better option is to fetch and store the images when needed with a technique similar to 404-caching

The component allows to modify the image url used in the components and modules templates

license users  can obtain code examples.