If you have problems with image previews in ranger, try using Überzug as image renderer. Common option is w3m and I just recently found out that some of the problems I had with images were caused by w3m, not terminal emulator.
After I started using Überzug basically every problem I had with terminal image previews disappeared.
I wrote short post about this to my blog: Even's DIY ‘n stuff blog
What made pick this? Just curious. I haven’t managed to find enough differences in gui file managers to prefer one over the other. Currently I like to use thunar. Nautilus is also ok but I think it need a lot of gnome dependencies to work, which might be problematic in non-gnome system. 