Board Thread:General Discussion/@comment-1475805-20151224012437/@comment-26290605-20160119223038

The Eye of Agamotto is likely the Time Stone, due to what Kevin Feige said. The Soul Stone, I think, will have something to do with Ragnarok. It lays dormant in the Nine Realms, and once it awakes, the cycle begins.

Also:

Tesseract

Hel (shown in Thor's vision)

Aether

Necklace

Orb

Solar Gem (sounds more fit for it's current location).