Forum:Wallpaper advice?

I keep trying to make wallpapers, but unless they're tiled I can't get them to work. I was trying to make a wallpaper like these wikis,

http://harvestmoon.wikia.com/wiki/Special:WikiActivity

http://avengersalliance.wikia.com/?redirect=no

http://deadisland.wikia.com/?redirect=no

Like they have a part in the middle that doesn't have anything and has pictures on the side. I don't understand how they can have a picture that big without going over the data thing. Is there a special photo editor that they use of something? Any help would be appreciated, thanks! Mai Is Me (talk) 23:13, September 21, 2012 (UTC)