Just in case anyone else renamed the admin folder, you will have to make changes to admin_login.html to make the images display properly on the login screen.
line 6
<link href="../admin/styles/admin_login.css" rel="stylesheet" type="text/css" />
line20
<img class="admin_login_icon" src="../admin/images/admin_login_icon.png" />
It looks like Boonex hard coded some paths in there.
We will make these paths more flexible in the version.