I installed the ‘Roshnilite Theme’ which is really wonderful. But I have a problem that there're some incomplete pictures on my home site as below picture shows. I cannot find where to set or delete it. Has anyone met such problem？
You may find that if you go to the Themes download page and leave a message for the devs of that theme you will get a more timely response. I am sure someone else uses the theme, but may not have had a similar experience. You may also be asked to provide further information, or be given a patch or a way of fixing your issue quickly. Alternatively, there may be an issue with the theme under certain operating conditions, or whatever. The devs are the most likely source of information here, sorry I can't help.
Moving to themes forum...
If this is on the Frontpage you need to switch the Course List to None in
Site Administration > Frontpage > Settings
Alternatively it could be you need to set up the images for your courses in the Roshenite theme settings...
Site Administration > Appearance > Themes > Roshenite (link)
Go to a particular course.
Go to Course administration -> Edit Settings.
Here, under Description -> Course summary files, you can attach images.
These images are displayed on site home page under 'Courses'.