Disable Featured Image By Default in Wiki Pro

Hi guys,

Is it possible to disable the featured image for all wikis by default? I'd like to be able to create wikis and have my users create wikis without any sort of featured image.

Unfortunately, if an image isn't added it just results in a large blank image area: http://conversantm.com/15rKa/4XSySSYc

Thanks in advance!

James