From the quick searching I did Krusader is tied deeply into KDE. It uses an app called krviewer. FOund this link that mentions this. http://www.linuxtoday.com/news_story...03-26-RV-KE-SW
Also went over to the developers site to check for faqs or forums. Seen you made a post over there on their forum site. That is a good place to get help on your question. Did you search the krusader forum on the subject?
Currently searching my drive to see if it is an external app called krviewer. Then I will see which package installed it. Current not an external viewer from the krusader package. So it may be built in app but requires KDE libs to function.
Well the results are in no file by that name. So at a lost there.
Does you system contain the KDE libriares?
One last thought is maybe the developer could possible create a patch that will use a different viewer other than krviewer.
No idea on your other question about thumbnails. Don't quite understand the question.