Default Image Viewer for FC

[Betim Deva]

I am building an rpm for a custom application and I need to decide
about a default image viewer for Fedora Core (ideally all versions).
Normally the application does a system call to invoke the image viewer
and display the images. User can still override the default viewer  by
setting an appropriate environment variable.

The question is: Is there any default image viewer that will work in
most FC versions, and in both KDE and Gnome by default in standard
installations.

Thanks