How do you change the main profile picture of a wiki page?

I happened to click on the "Exploding barrel" Concept page and noticed that the main image that is being used, which is lifted out of Half Life 2, is a nice picture of the gravity gun manipulating a barrel, but I'm pretty sure it's a normal barrel and not an exploding barrel which kind of defeats the point.  There's a perfectly good still shot of an exploding barrel in the other images that are shown on the right of the page in the images/screenshots section and so I thought I might swap this out for the main picture that's being used at the moment, but I couldn't see a way of accessing the main picture from any of the edit buttons.  Anyone know of a way to do that, or is the initial main image that is chosen for a page always going to stay the same?

When you are in the Images page, hover over the image you want to select with your mouse cursor and buttons should appear right below it.  There is one called "Set this as main image of _____".  Click that button.

At the moment you cannot, only site moderators can. I think they will/might eventually implement it so we can edit that part as well.

"When you are in the Images page, hover over the image you want to select with your mouse cursor and buttons should appear right below it.  There is one called "Set this as main image of _____".  Click that button."

Yeah, since all of the Wiki profile pictures are pre-set, I think only mods can edit. Which is kinda annoying.