I have noticed a large number of pictures on a screen (or even one very large one) can cause a project/screen to take a long time to open.
This can be sped up noticeably by the simply presizing your pictures. That is saving them in the same size they will be displayed at.
Any scaling of pictures required is done on the client after it’s downloaded from the gateway. If you have the same image many times on the screen it looks like each time it is displayed it is resized. If your client is a older box it becomes very noticeable.