(Disclaimer: This post was originally written by me on the ThemeForest Community blog in 2012. It was deleted in the mean time but the content is still relevant in my opinion so I’m re-posting it here. I hope you find it helpful.)
If it’s the first time you are making a theme for ThemeForest it might be difficult to get approved, but it’s not impossible. The standards are really high these days, but if you really want to get approved you will.