I used to use Tweetie, but never on an iPhone. On my computer I always uploaded pictures to something like Twitpic. Since my Twitpic account and my Twitter account were synced, anything I posted on Twitpic would post as a tweet. As for following, you have to actually follow the person on Twitter before their posts will show up in Tweetie. I think you can search for users from Tweetie, but I don’t exactly remember. It’s been a while since I’ve used Tweetie to be honest. I hope this helps some.