If the picture is selected when you insert the bookmark, the picture will be replaced by contents of the clipboard when you use pastespecial.
The following illustration displays two bookmarks, indicated by [ ] which will be visible if you select the option for bookmarks to be displayed.
The smaller set of markers inside the table cell represent the bookmark that will be created if the cell is selected.
A screen capture of that table was then made using Snagit and inserted into a document as a picture and then while the picture was selected, a bookmark was inserted which results in the display of the elongated pair of markers.
With bookmarks of that type, the contents will be pasted inside the bookmark, replacing whatever is there.
I make use of that feature in the Merge with Charts utility in the
MergeTools – 20130627 Add-in that I created that you can download from the following page of my Windows Live SkyDrive:
https://skydrive.live.com/?cid=5aedcb43615e886b#!/?cid=5AEDCB43615E886B!cid=5AEDCB43615E886B&id=5AEDCB43615E886B%21566