Edit Design > Extended Settings
I think you may want to see a logo / header in your website. For this, firstly you should upload your logo. After uploading, click 'Edit design' button, then click 'Extended settings'. You will see 'Header picture' option under the boxes. Choose the image you have uploaded for the header. Lastly, click on 'save' button. After all you have your own header in your website.
1) Every layout may not have 'Header picture' option!
2) The layouts which have 'Header picture' option want certain image size(s). For example: The logo should be 921x104 pixel in the Iceblue layout. It means if you use Iceblue layout, you should edit your logo in 921x104 pixel before uploadingClick here for seeing header picture's sizes for layouts which have that option.
3) Before uploading you should deactivate 'Downsize the pictures' option in the manage Images page. If you don't, image repeats again and again, or seems smaller than you have edited.