Loose leaf tea is the best way to make iced tea. The tea used in most tea bags is the "dust and fannings" from broken tea leaves that have lost most of their essential oils and aroma. When steeped they release more tannins than whole leaf tea and the result is a bitter and astringent brew.
Any tea can be iced by adding a bit more leaf so the ice doesn't water it down. Follow the same steeping instruction and enjoy!