This is in the info box when uploading a game:
Note: If the game has a screenshot and you want it to appear in the slideshow on the the front page, tick the 'Promoted to front page' check box located under 'Publishing settings'.
Nowhere, on any page, can I find "Publishing settings" or the option to "Promote to front page".
What am I missing?
On the very bottom location of the 'Add game' (or 'Edit game') page,
click the triangle 'Publishing Options' to see the option requested.
There is nothing there.
The words "Publishing options" appear once on the page and only in the info box at the top of the page. 
Hi there. Just realized that only moderators and admins can see this checkbox. I will be able to give everyone access sometime in the future, but in the mean time I have promoted Rose Garden to the front page for you.
So I'm not crazy then, huh? 
No, I was crazy. 
And before (or after...) you guys think I'm a bit narcissistic, I was under the impression that the promote option allowed me to choose which screenshot is displayed when the game is shown on the main page. I didn't realize that this is how the games show up on the main page. 
I don't know whether the promote option allows to select which screenshot will be shown.
You can choose the main screenshot by dragging the desired file to the top of the list in the edit screen. At the bottom left there is an icon, or your cursor will become a glove.
