To set default custom logo to appear on all the events created in your account, click your username on top right corner, from drop down menu click Account Settings. Set straight link to image on Logo URL field.
Now all your events will feature this logo instead of Loquiz logo. This default logo can be overridden by defining custom logo for each event. In this case event specific logo is used.
Logo is shown on mobile devices in application and on results pages. Loqo image is scaled down to 300 pixels longer side in the app.