Why are deleted images still appearing in my product collection?

[Upz]

Hello all,

When I first set up Shopify, I used the same red image for each product in my collection. I wanted to quickly get an overview of how the images would show up. Since then I have removed the red images and imported my real product images.

The problem I have now is that those red images still show up when I first go to the website while all images are loading up. Even sometimes just for a split second. 

Please have a look: www.upznshit.com / Password: marie

Does anyone have an idea why this is happening and how to prevent it?

Thanks