After adding a white trim and a drop shadow to the images, we're finally able to add the glossy texture.
Activate the 2nd layer with the image on the bottom of the stack. Hold the Ctrl key and click on the thumbnail of the layer. This should create a selection of the layer.

Set white as the foreground color. You can easily do this by pressing D to reset the foreground and background to the default colors then pressing X to switch the foreground and background color.
Add a Gradient Fill layer (Layer> New Fill Layer> Gradient Fill). This should appear above the selected layer and the layer mask of the Gradient Fill layer should have the layers shape as its layer mask.
A Gradient Fill window will appear. In the window, change the Gradient to Foreground to Transparent, style to radial, and scale to 150%. Uncheck and check the Align with Layer checkbox to see which effect you like more.

Repeat the previous steps to create a gradient fill layer for the rest of the layers.

Activate the Elliptical Marquee tool and create a selection with a bulge. You may need to zoom out (Ctrl+-) to get enough room to draw the selection.
With the Elliptical Marquee tool still activated, move the selection so that it covers about half of the top image. Select the layer mask of the top Gradient Fill layer and press delete.

Repeat the previous two steps for the rest of the layer masks.
