Using thumbnails in treeview

Tree view items can show thumbnails as an alternative to icons. Thumbnails are best used when a user needs to have a preview of the content represented by the tree view item. Icons can be used as a fallback for when an image is unavailable, but should be appropriately sized to match the thumbnail.

Be mindful of thumbnail size and proportions

Tree views with thumbnails should use a thumbnail size that is appropriate to the size of the tree view itself. For example, an extra-large tree view would not work well with small thumbnails; those proportions may be better suited for using icons instead.

Multiple thumbnail

In some cases, multiple thumbnails need to be displayed in-line with the tree view item (e.g., layer masks). These thumbnails should be individually selectable and inherit all other behaviors of a standard tree view item, such as drag-and-drop behavior. Don't use more than 3 thumbnails per tree view item.