You can be tempted to use delay() again. But using delay() is generally a bad idea, as everything stops for the duration of the delay. Actually, you rarely need to use it, except when dealing with system (getting serial data, etc.). Often, you want to do something else than displaying the images, so you need to keep running the frames at the normal rate.
delay() have been so badly misused that the Processing designers decided to remove it from the version 2.0... (perhaps it have been moved to the Serial library).

How to display the images for some time, then?

It is simpler than you might thing: you display the image, and count the time: you check on each frame how many seconds went since the last display. When a given amount of time is spent, you can display the next image. For this, you use millis() to check the time. An example follows, illustrating this common programming scheme: