Very very nice.
1.Pebbles in the blocks, ribbon in the sashing and boarders.
2.No
3. White would look more formal, random colors would look cutsy(, and in this case, would make the quilt look less like artwork. (I would go for the formal, artwork look in an entryway regardless of haw informal my house was.)
Note: Use an 80/20 batting for a wall hanging.....and add weights as paper princess says