There is no tool in the Mercurial ecosystem that is going to give you a visual tree of ignored things. You could, however, do something like this:
cd ..
cp -a yourRepo ignoredOnlyRepo # create a copy (not a clone) of the tree
cd ignoredOnlyRepo
hg status -mardcu --no-status --print0 | xargs -0 rm
That creates a copy (not a clone) of your repo and then deletes all non-ignored files from it. At that point you can use any file viewer you like and you're seeing only the ignored stuff because they're all that's left.