Hello Rajarama!
I followed the steps to change my logon image both: 'SAPNetWeaverLoginTitle_wo_Subtitle.jpg ' and 'NetWeaver_Default_Picture.jpg'.
I followed the route showed in your images and click on the object 'SAPNetWeaverLoginTitle_wo_Subtitle.jpg ' then make a right click and select: Upload/Download > Upload and Replace; after that I click in the refresh icon.
After that I went to my logon session and still look at the standard images, did I miss any step?
Any help will be greatly appreciated!
Regards,
Sue Mak