I don't think it will be displayed (banner) when you invoke SQL*Plus. (Currently I am not working on Oracle EE).
It might already have been there. Check whether there is a possible syntax error or privilege problems in creating the object.
Also, I don't think its necessary to have the compatibe level set to 8.1.7 for OBJECT option to work. I guess, even the 8.1.5 compatibility will be fine, though the highest comaptibility is recommended for taking advantage of the new features.