Lightbox options

Please go to “SEA Theme > Theme Options > Content” tab, set to show/not the button in the lightbox:

You could set the lightbox skin, it supports the dark and light skins.

If the image was set the caption in the Media Library:

The caption will be shown under the image:

Please use the custom CSS(“Appearance > Customize: Additional CSS”) to adjust the caption text style:

.pswp__caption__center {
    text-align: center; 
    font-size: 13px;
    padding: 10px;
    line-height: 20px;
    color: #CCC;
}