It's not a question of how the images are posted, the issue is the shear number of images you have on the page.
Before the CSS can be applied to the design, all of the media has to be downloaded to the client browser. Only after all of the media is being displayed can the css style be applied. because of the number of images on your page, there is a delay while they are being downloaded before the css can be applied.
To use SiteAssist Pro, the design of the site would need to be re created from scratch.
