Determining the Center of Interest
Each painting should have a center of interest, or at least areas more defined than others. That area may have one or more attributes like:
These attributes diminish as they expand outward from the center of interest, like concentric rings in a Bullseye.
Try to Find the Bullseye
Hover the pointer of your mouse or Tap your finger (on an iOS device) over the painting until the center of interest reveals it's self.
(hint: Look for the attributes as mentioned above)