When a tree view is drawn, it must provide enough room for any images associated for each node. The size of the first item image added to the tree view data type is used when drawing the tree. For example, if the first item image for the tree field is 20 by 20 pixels, an area that size will be used for every node. Images of other sizes are scaled to fit in the area provided. For the best appearance, we recommend that all images in the tree view be the same size.
Images used for nodes are typically 16 by 16 pixels.
State images are always 16 by 16 pixels. If you will be using state images in your tree view field, we recommend that all of your images be 16 by 16 pixels.