Introduce offset for loading images, to avoid render lag

[klinker24]

Addresses the concerns in #53.

This will offset the image loading, for each image, to between 750 and 1250 ms.

@Serubin want to test this and let me know if you see a difference, or if you would recommend a different approach?

[Serubin]

This looks great. I added a fix for an unrelated (but somewhat related) issue in. I'll test in other browsers and merge!

[klinker24]

The loading text is much better now, thanks!