Just discovered a new twitter background maker called twitbacks. They’ve got free and paid versions. I wasn’t too happy with the results when I created mine so I went back to my standard Hawaiian palm tree background I’ve always used. But, I know lots of people who swear by this service so you might try it when you get the chance.
You can also google “twitter background maker” to find other free services. In any case, I suggest using a custom background rather than twitter’s standard backgrounds cause it’s a cool way of branding your camp.