It is possible to modify both icons on speed dial (per report and per section) and to change the set of featured reports - see config/dashboard-rtm.properties. However, those modifications are not officially supported and your changes may be overwritten by the upgrade.
Changing order is only possible in the Featured tab - see config/featured_reports.conf. Favorites are sorted alphabetically, and All reports are sorted alphabetically first by section name, then by report name within section.
Thanks Karolina and Sebastian. I won't modify the icon of build-in report but want to change my own DMI report. So is it possible to change the icon of my own DMI reports which put in the "Favorites" section?