The answer depends on the template on which your application is based.
If it is based on the legacy navigation template (displaying perspectives/views as in this screenshot - as do most of our sample applications), then the area outside the view, is not controlled by modeling, and you'll need to change the look and feel of the client (defined using html and css). There's a specific discussion of the logo in here and more details regarding client customization here.
If you've used one of the newer templates (such as the newer default, empty template), in which the entire page is controlled via modelling (this site is one such application), and you're having trouble with using the Display/Image template, have a look at this thread.
Please let us know if you need any additional help or calrifications.
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