Prefetching images by having Opera for Android anticipate where you might go and grab every image from each page before you visit a page?
That sounds like a recipe for excessive data usage (even risking banning from sites that assume these prefetches are DDoS attempts). However if you want a quicker display of images, this will depend on how websites set up their image displays.
If a site has terrible image loading, either they are having server issues or they don't have good coding for loading images. You may have to contact their webmasters and ask them to speed up image loading for their domains.
Also if a website with good coding uses third party services (including for adverising), this can slow loading of websites and their images. There's nothing Opera can do about websites that poorly code or have bad servers or websites that use third parties that poorly code or have bad servers.
Also with Opera Mini's proxy and compression service, not much data is used which result in quicker image displays, however Opera Mini doesn't prefetch all images of domains you might visit.