No customizable forms yet in Jobroller. However, this can be implemented through custom coding. The theme is not encrypted and so it can be modified accordingly. It just depends on your coding skills or you can just hire a coder to assist you on its implementation. Appthemes also have certified community partners
http://www.appthemes.com/partners/ that can be contacted for customization jobs.
However, this has been requested already at the Ideas Exchange page
http://ideas.appthemes.com/jobroller...?orderby=votes of which implementation depends on the number of users voting for it.
Yes, job posters can upload logo and or images in their job listings. You can check it on the demo page here
http://demos.appthemes.com/jobroller/submit/.