Not as far as I know.
You could write a script that uses New Window to open your own "calendar" control in a small floating window. Then you could include your own image, but this is a lot of work just to add a different "look" to the calendar control.
Do you know of any calendar control available to do this with.
No I do not. You can web search for FileMaker plug ins, you never know what someone else may have produced until you look.