I've successfully created my own login screen, by modifying the web.config to point to our login page as well as when users login into the Sitefinity CMS to redirect to the same login screen
To do that I followed the directions from this post: http://www.sitefinity.com/support/forums/sitefinity-3-x/developing-with-sitefinity/sitefinity-login-page.aspx
However, if I click the log out button in the CMS, it redirects back to the Sitefinity/login.aspx page. Looking further inside the Sitefinity/Admin/Admin.master page, it simply does a redirect.
|protected void logoutButton_Click(object sender, System.EventArgs e)
To make this all work, I've modified the Admin.master page to use the LoginURL property (similar to what each individual page does in the CMS)
Would it be possible to modify your code for next version to use this property instead of just hardcoding login.aspx?