Certain themes create a mouse-over effect on every picture of the site that links to somewhere. JIG is no exception from this JavaScript trickery. However, it can actually be nice to get a coherent look with the rest of the theme. It's advised to disable JIG's own overlay, icon and special effects so you don't end up with multiple mouse-over effects stacked on top of each other. Themes usually add an icon and fade out the thumbnail a little bit, or add a color overlay layer. The extra code injected by the theme can be disabled with Custom CSS (only over JIG elements). In order to find that, you need to be familiar with the base layout of JIG or how themes work. So, if you wish to get rid of the theme's overlay effect, contact JIG support and the solution will be provided at no extra cost.