I found this for sale in the British Museum gift shop today. As you can see, the bookend is described as being that of an ‘Egyptian king’. I am not sure why the label is being so coy; the real bust is on view in the room next to the shop and there it is identified as being Ptolemy I Soter.
I have to admit, I don’t know why - the image is a generic one and there does not appear to be any writing on the bust to identify the king as Ptolemy I but I am sure the museum has its reason for making the identification.
That aside is it appropriate for images of kings to be used for trivial purposes? Of course not, but given Ptolemy’s sideline as a historian of Alexander’s expedition, a new career as a bookend does seem very appropriate, after all!