How to display Logon page branding images uploaded in KM without any authorization

Dear Experts,

Is there any ways to display Logon page branding images uploaded in KM without any authorization.

I am using portal 7.3.

I have uploaded the branding images in KM folder and also given the permission for Anonymous Users Group and Anonymous user with full control.

Then I have given the URL to these images in nwa/auth.

But when we try to access portal Logon page, it is asking for authorization. Even if we give the URL to the images directly into the browser, it will ask for authorization.

Is there any other ways to give permissions to the KM Documents so that it wont ask for authorizations again.

Thanks and Regards,

Suman I Kurian