I can see you have removed the login button on your login page. well done then. We are making it way more easier to take control of the theme of your Tribe in future.
Pretty much the interface of any webpage can be tweaked by modifying its css properties. It is fun and pretty easy. So if you have an interest in tweaking your community, knowing how to inspect an element and change its CSS right within your browser would be quite an added skill. you can also easily change other aspect of your web page without asking for specific instruction. a quick google search would bring tons of result.Having said that, We are planning to equip Tribe with settings that would allow you to modify your community right out of the box without touching code. Till then, the work around is with CSS overrides. However, if you change every aspect of your Tribe using CSS overrides, future updates of Tribe might break things as it might not be compatible with the changes you have made and you may simply need to remove that additional css. So any instruction in regards to CSS changes on Tribe should not be taken as an official guideline for doing things in your Tribe workspace.
There is general class being added to all of the pages <body class="role-guest"> so you would be able to target elements on the page for non logged in user via css.