You can view certain photos from your iPhone on the watch. By default, your watch displays the photos you've tagged as favorites, but you can change the album. To do this, open the Watch app on your iPhone and go to the My Watch section. Tap Photos and change the Synced Album to one of your choosing.
On your watch, open the Photos app to see thumbnails of all your synced photos. Zoom in by tapping or turning the Digital Crown. Swipe left or right to browse through them, and tap a specific photo to see it up close.