Currently Being ModeratedJan 11, 2013 2:19 PM (in response to Bakkergh)
That's the icon that the version of the iPhoto application on the other Mac applies to the libraries. Can't be changed.
Currently Being ModeratedJan 11, 2013 2:49 PM (in response to Old Toad)
Thank you for your prompt response.
All libraries on both my computers had the original icon. After copying one library from my MacBook to my iMac, now both computers have received the new flower icon on all libraries!
However, the photo libraries work as usual, with no problems.
Currently Being ModeratedJan 12, 2013 2:14 PM (in response to Bakkergh)
I simply replaced the flower icon of all libraries with the original icon on both computers and now everything is back to normal!
Remains the question why all icons were changed.