We've recently looked into the number of tags per icon and decided that we would move the limit from 7 to 9. You can always add more, but adding more than 9 tags will slowly decrease the rank of the icons, so only add more if you believe they are really relevant.
Also, the report for tag issues has been updated. We now show a warning if the average number of tags per icon is less than 1.5 for the whole icon set. And a warning if the individual icons have more than 9 tags.