When I'm posting a link to a facebook page, facebook pulls images from the page and puts them on a carousel. The images it pulls from the site display nice large previews, see below:

However when I upload an image, it only shows a small link preview image. Anybody have any tips on this?

The image size I uploaded in this example is 600 x 454 px, so according to the following article on this matter, it should be loading a big preview.
http://superspicymedia.com/blog/how-...umbnail-image/
Use 476x249 as your image size. Works perfectly unless you're wanting to run Instagram too.
Hit the publish button 
When creating the post, image is small in the preview, once you publish it, it will change into the large one. Not sure whether it depends on the image dimensions, but that's what happened to me with the last few posts I published with an uploaded image.