How to set image css property in libary?

We have various images in an image library.   How can I set the css property of  a particular image?  It seems I can only edit the title and alternate text.

Found about setting custom fields for content types.  Added a Css field to the images content type.  See docs.sitefinity.com/edit-an-existing-custom-field. 

Hi hooman.  As i right you understand, you want to add custom field for image.

You can do it in this way:

1.  Go to SF backend
2. Go to Content->Images
3. Click Custom fields (in the right sidebar)
4. Create custom field (ex. name CssClass)

And after that you need to edit widget designer. Example for feather:

1. Find template inside your resource package /Mvc/View/Image/Image.cshtml or create new one
2. Add  @Model.Item.Fields.CssClass

Template should looks like this: