As stlucia as already pointed out just create more slides containing the "credits" via your Image Editor, Obviously this will mean creating a new DVD. It's a long time since I used Easy CD & DVD Creator, so I cannot remember if you can control the individual length of a particular slide, which may be necessary if your additional slide contains a lot of detail.
What I recommend you do is download the trial Proshow Gold software, which allows you to do all this within the program. Having used many slideshow progs I can honestly say Proshow is without doubt the best. click here