The hand in the artwork represents our Father in Heaven, who protects us – as represented by the globe. The colours dripping away from the hand represents the evil things of this world.
A promise is always most treasured when you are down and out. When you are at your lowest, you cannot imagine happiness. That is why we need to have a mental image that gives us hope. Israel had been in exile when Jeremiah gave this promise from God. So I imagine that their mental image is the land which was promised to them in Joshua 1 – where God promises to bring them back to their homeland.