Heap will re-calculate a heatmap each time you load it (from a saved chart, or from a different browser). This might mean that your background URL image might look different than the last time you viewed it.
For example, let’s say you run a heatmap over 7 days for any product details page in your eCommerce store. When you load the heatmap first, the randomly selected background image might be the URL for Product 1, but the second time you load a heatmap, the randomly selected background image might be for Product 2.
Note that the heatmap overlay (the hotspots, scroll colors, etc.) should stay the same if the heatmap query hasn’t substantially changed; it’s just the background image that might look different.