This full-fledged feature is on our roadmap...meanwhile..
There is a simple temporary way to do this:
Crawl just 1 page of any URL. ( set the Max Pages = 1 )
Upload a new page design to the home page like so.
Add New Child Pages and Directories
4. Upload new wireframe / design images into the page(s) + edit the page Titles and/or new directories.
DONE!