Today Turbine announced that the new featured instance rewards will only be for characters level 100+.
“Once per day, when you complete this instance at level 100 or above, you will get a box filled with extra rewards, above and beyond what you normally get from that instance. From level 100 to 104, this extra reward will primarily be Scrolls of Empowerment. However, if you run an instance at cap, you also get a chance to loot a piece of gear exclusive to the Featured Instance system!” – source
Turbine also announced that there will only be 6 instances in the system at the start.
The following six instances are the first six instances that will be a part of this system. In future updates, we’ll occasionally change up which instances are represented here, and we hope to eventually have all of the best instances in LOTRO be Featured. – source
The six instances featured include: Halls of Night, Inn of the Forsaken, Ost Elendil, Sammath Gûl, The Bells of Dale, and Ost Dunhoth – Wound & Fear Wing.
You can learn more about the featured instance system by reading the new Developer Diary.