1) You don't have a search. You have four filters, three of them with over 20 choices each. You've well over quadrupled the number of choices a visitor has to make before they see any results.
2) You don't let me quickly browse a list or grid of themes. You show themes one at a time, which feels like the slowest possible way for me to find a theme.
If you can fix your UX, something I'd think about for your marketing is talking about how many additional (quality) themes people will get a chance to see. I buy or recommend themes to buy for clients pretty often, and I pretty much only go to ThemeForest. My impression is they have the largest collection. If you can convince me I'm going to get a lot more good options, from one place, and be able to evaluate them as easily as I can on themeforest (reviews, Wordpress & browser version support, etc.), I'd be interested.