All themes but the Vintage theme will allow you to add a logo to your menu. The logo will display on the left within the menu, and you will be able to set the menu items at left, center, or right-aligned.

To set a logo to display in your menu, select Site Configuration from the admin menu, then select the Select Logo button in the Branding Information section and upload your logo image and select it (it is recommended that the logo size is no more than 120 pixels tall and no more than 300 pixels wide):

After your logo has been selected, navigate to the Theme area under Site Configuration and select the Change button on the Menu Style area:

Select a Menu Style that includes a logo.