Multiple random images per page, without repeat

So, I need to display 2 or 3 different images in a website, as simple parallax dividers for content. I have an array of 4 images, so I'll be able to randomize without repeat them in the same page, althoug the random won't be that noticeable. I've lurking this for a while, and found these Random Image Display, Without Repeat, with Javascript | | http://ift.tt/1oYAbBA | | http://ift.tt/1RnIGMQ but they didn't work for me, so I decided to start a new topic, because I'm really newbie (actually, I don't know writing nothing at all) at javascript, and can't figure out what's the best approach. I understood it would be something like randomize the items, assign each of them a position (a number, a character, a [i], etc), and then call for it in my php page. Could you guys please help me?