In older configurations, I used the Image size limitation, because users used to post images larger than screen's resolution. But when a post had a lot of images, this crashed the system because of the high amount of memory this feature used.
Nowadays, I am using the thumbnails d that you can configure while going to
ACP -> Main settings -> message's images.
I have configured the thumbnail for 540 px, this way users can see normally the images in low quality but quality enough to take a first view.
I have activated too the HighSlide JS feature, because this way users can take a look at image in full size, if they want.
This was working ok at the beginning (from 2-3 months until today), that now, when you click one image, it is showed with HighSlide, but if you move to next image, only a small white square is showed.
I thought that maybe there was a large amount of thumbs, so I tried to clear the cache at the wiper on the main admin screen, but the problems keeps being the same.
At the beginning it worked without problems, even if the post had a lot of images. Today it is failing even with two images.
You can take a look at the problem here:
This is working bad on Safari 5, but working ok on Safari 6. As you should know, Snow Leopard does not allow Safari 6.