As far as I know, the DOpus viewer only shows the largest format (size) inside an ICO file. It would be great to have a plug-in that could show all the ICO formats (sizes) in the viewer.
I'm not a programmer, so I can't create such a plug-in myself. But perhaps there's someone who could create it? I really don't know if it's a lot of work and I also don't know if there are
other people who would like to see such a plug-in ... 
Or do the Stellant viewers already have this functionality? Something like this would be great:
I'd like that too.