It doesn't matter where you put such feng shui 'items'. There is no such thing as a 'right' or 'wrong' place for any of these items, or ANY items for this matter. This is because REAL Feng Shui does NOT involve the placement of 'objects' or 'lucky items'. These items you are referring to are probably made of plastic from a factory in China, they don't produce 'Qi'.
In Feng Shui, the primary concern is Qi Flow. And Qi Flow comes from the external NATURAL environment, flowing into your home. To measure the quality of Qi, we consider the sector, direction, natural environmental feature, the layout of the building and where YOU are in the building - if you are tapping to the Qi, or not.
Hope this sets your mind at ease.
Warm Regards, JY