After a request from Scott Widick, I have added a new position to Theme 3 in the top left corner called Header. This means that you can now go to Blocks and add a new block the the header region and it will appear in the top left corner. This is extremely useful if you'd like to add your own custom logo or your own text and want more control.

Note, that by default the Site Name and Slogan which you enter into the Site Information screen occupies the top left area, as well as the Logo you load into the themes Configuration. If you use the block in the header position instead, it is suggested that you uncheck including the Site Name, Slogan and Logo by going to Themes and then clicking on Configuration next the Theme 3. This will remove that text so only your block info appears.

If there's any questions on this or other suggestions, let me know!