If you want to associate image files with the Opus viewer then that is easy. See the FAQ: How to use the Opus image viewer outside of Opus
If, instead of the Opus viewer, you want double-clicks on image files to open a new Opus lister with viewer attached then I don't know of a good way to do that. The command Go NEW=viewpane PATH="%1" comes close -- it opens a new lister with the file selected and the viewer open -- but the viewer doesn't show the file until you click on it or push space.
I'm guessing/hoping you meant the first thing not the seocnd. 