Slideshow Parameters

You can use the autostart shortcode parameter by switching from the Visual to the Text editor. You will then be able to add that parameter to the gallery shortcode, like so:

[gallery type="slideshow" ids="1499,1477,1437,1436" autostart="true" size="thumbnail"]

autostart, as you’ve probably guessed, ensures that the slideshow starts switching from one image to the other as soon as you load the page.

size, on the other hand, allows you to specify an image size. In the example above, I used the thumbnail size:

Thank you Jeremy!