Block with single image at top
You can have another view which selects that image. Then on your existing view you can add a header and choose "Global: View area". Then you just select the view you created earlier and that's it.

Another solution would be to have just another views block displaying that image.

The third solution would be to add an attachment (under Displays click Add > Attachment) instead of a new view block. Choose the fields (image in your case) and attach this (look for ATTACHMENT SETTINGS section) to your existing one.