Grouping by an image is not really possible because two rows with the "same" image actually have two different instances, i.e., Image.Equals will return false even though they contain the same graphical data, because they are two different instances.

There are a few different ways to handle this, the easiest of which is probably to persist an integer or string that identifies the image rather than the image itself, and add an unbound column for the image data. You could use InitializeRow to read the persisted number/string, use that to determine what image to display, assign that image to the unbound column, and hide the column that contains the persisted data. This approach has the benefit of not persisting redundant image data, i.e., if you have 100 records with the same image, you don't want to keep 100 copies of the image data, just something that identifies the image.

To group by an image, you would have implement IGroupByEvaluator (no big deal, only two methods) and assign the implementation to the image column's GroupByEvaluator property. Your implementation would look at the column that holds the persisted number/string, decide which image that corresponds to, and group according to that.

If you need us to provide code samples for any of this just repost and someone will help you out.