[forbes]

I'm one of the guys who built ThemeForest. (I don't work at Envato any more.)

I built the rollover previews on that site (which has been rebuilt and improved many times since). I can tell you that you are going to have trouble keeping the preview in view when they are as large as the ones that you are using, whilst still making it possibly to see the other icons in the grid. You'll need to flip it left and right, up and down depending on the position of the mouse.

I also think you need to think about what value you are providing. I think a curated site with less themes with proper reviews would be much more useful than just a scrape of the thousands of themes out there. Your own reviews would be original content which might have a slim hope of outranking the actual themes themselves in Google results. Without that, I don't think you will get a lot of traffic.

Good luck.

[csomar]

I'm aware of the rollover preview issue but didn't have the time to fix it. Indeed, it's not simple but I think it was covered in many tutorials, so I won't have to reinvent much of the wheel.

As for the value proposition of the web app, I'm still unsure about it (in the discovery phase). I'll be trying different things and checking their output/ROI. Manual reviews of themes, hosting reviews, building a user community...