The logo showed at login page, and others, is not enclosed in any meaningful element, to be able to configure styling with css:

<a href="<?php echo config_get( 'logo_url' ) ?>">
    <h1 class="center white">
        <img src="<?php echo helper_mantis_url( config_get( 'logo_image' ) ); ?>">
    </h1>
</a>

Ideally, this should be enclosed in a div that can then be overriden with a custom css, for example, for positioning.

My specific requeriment is to place this logo in the right upper corner, with customized margins.