Problem: Preview doesn't update when changing a layer's symbology
The Preview tab doesn't show changes to a layer's symbology.
The Contents tab is not selected.
Solution or Workaround
When changing the properties for a layer file (.lyr) in ArcCatalog, make sure the Contents tab is selected. This allows the layer file's image to be updated properly when displayed in the Preview tab.
If the Preview tab is selected, and you make changes to some layer properties, the preview image will not updated automatically. In this case, select the Contents tab, then go back to the Preview tab to see the correct image.